Finding the directory for Daz Studio
OK, here's what happened. I downloaded Studio into a new computer, installed it, and tried to use Daz Central for the first time. It was way too slow for some reason, and kept stalling, so I used the Daz Install Manager. It kept failing
, which as we all know is frustrating, so I figured it was probably just a slow day on the wi-fi. Now Daz Central must have downloaded assets into This PC-Windows(C:)-Daz3D- Applications-Data-Daz3D-MyDaz3DLibrary, which is where I eventually found them when something happened that I will explain later.
We all know the DIM automatically put all your assets into Users-Public-Public Documents-MyDaz3DLibrary, which was always the wise choice, since you should not clog up your Application folder with gigabytes of assets. The Public Documents-MyDaz3DLibrary folder is still there, except the folder is empty because Daz Central put the few downloaded assets it managed to get into the Application folder. Unbeknownst to me, this setup worked fine, in the sense that the program could find its assets, but things were about to get tricky.
There were a few assets I bought from Renderosity, which have to be installed manually. I looked to install them into the Public Documents folder, but that folder was completely empty, so I searched for where all my assets were downloaded and eventually found them in the Application folder, something that's never happened before, but thinking it was the "new" thing to do, I put the Renderosity assets into the same folder. Well, guess what, they didn't work properly. Somehow, the assets "knew", or refused to work properly because they were not in Public Documents!, because, of course, there was nothing in that library to draw from. Daz Central put them into Applications, so I dragged all the assets from the Application folder and dropped them into the empty Public Documents-MyDaz3DLibrary folder, effectively transferring all the data into what once was the proper folder for all assets. But now Daz Studio cannot find it. Obviously.
There used to be a way to redirect libraries; you could tell your program where they were and you could put in the new "address," and all would be well. So...where is that window that allows Studio to find the correct directory and draw from there in perpetuity?
I hope I made sense. It's kind of complicated to explain and yet it's not complicated. How do I tell Studio where the correct directory is? Maybe I should have just said that. 
Thank you to all the fellow Daz geeks and nerds out there, who know the vaunted answer.

Comments
Is Edit > Preferences > Content > Content Directory Manager what you're looking for?
Content manager is definitely how you should point Daz Studio at the files.
As an aside, I would recommend putting items from shops other than Daz Studio into the C:\Users\<your user name>\Documents\DAZ 3D\Studio\My Library rather than mixing them up with the Daz-installed content. This can avoid DIM and Daz Central from breaking non-daz store content as well as protect the other store's content from things that DIM or Daz central may try to do.
FWIW, your assets should work no matter where you put them, so long as you link the folder in DIM, EXCEPT the application folder. And the reason they aren't working correctly there is because of Windows and UAC and not DS. Not sure why they were put there...I've always had DIM wanting to drop them in Public documents, unless someone changed something on the Daz end. I have everything on an external drive (assets, backup zips, thumbs and manifest files), so I always changed that in DIM ;)
And I would recommend putting your content on another drive than C, to avoid filling that up.
Yes, that too. I actually keep mine on an external server under a different drive letter. I should probably have noted that as well.
To Butterfly, Chezjuan, AlienArt, and felis,
Thank you all! Yes, that did it.
I had gone into Preferences, but I obviously did not look deep enough, and missed the Directory button at the bottm of the list. I was able to change the address so that Studio could find the new directory. And yes, that is a good idea to put assets into different folders for Rendo and Daz. I never thought of that, and of course, putting them all on an outside portable drive is not a bad idea either; it would save on space. I will look into that.
Thank you all again for your quick and kind responses. I really, really appreciate it!
Moonbaby
Could not agree more and not just because of C-drive filling up, but also because the filesystem on the C-drive is the most vulnerable to corruption and the Microsoft created folders have restrictions and other undesired side effects (such as Onedrive taking over)
If you use Daz Central first it will use a single folder for everything, split into sub-folders. Its applications folder is not the same as the protected Applications or Progam Files folder. If you then install Install Manager it wil keep the same locations. Similarly, if you install Install Manager first it will use its defaults and if Daz Central is installed later it will keep using those rather than its own defaults.
To PerttiA, Don't you just hate One Drive! It's so intrusive and insidious. It constantly tries to take over your computer. Changing to a portable drive is looking better and better. Thank you for the thought!
To Richard Haseltine, I didn't know that. Good to know now. I had never used Central before because DIM worked just fine, and I didn't see the point of adding another application, but I was having a problem getting the latest Daz version and it seemed that it was only offered through Central; at least that was how it appeared because I couldnt't get it any other way, not even through DIM. That was why I tried it, but as mentioned, it took forever to download stuff. I checked downloading from other sites and they downloaded fast, so it wasn't my wi-fi, per se, which is the excuse I gave it; it was Central that was choking the download. Either there was high traffic in that moment, or a deliberate short bandwidth for downloading. You can notice this on other sites where you can only download one item at a time, like Sharecg; they choke the bandwidth. Dissappointed with Central, I went back to using DIM, but it suddenly kept failing to download and install, probably for the reasons you just mentioned - which ever app gets used first has the power and Central had been first, and it messed up DIM, so I uninstalled Central. It had a snappy interface in comparison to DIM, but who needs it? I thought it would be able to compartmentalize things, like people, props, scenes, but, NO, it was a very limited inteface. I'm more interested in performance. DIM could do multiple downloads simultaneously, and just keep going until the newest items were downloaded and installed; not my experience with Central. But, it might have been a bad day for the internet, right? We will never know, because I have no desire to ever use Central again. And when DIM times out someday, which it will as Daz Studio has to reshuffle its programming (Qt, anyone?) to a more advanced level at some point, then I will just manually download assets and install them myself as we do at other sites like Art Station, Rendo, and the like. As in life, all things are a process... Thank you, Richard, for the clarity.