Select your garment in the Scene tab and then click on the lines icon at the top left of that tab. Choose Assets/Transfer Utility.
In the Pop up window choose Genesis for the Source Item and your garment as the Target Item.
If you have modelled your garment around V4, shape Genesis to V4 and choose Current in Item shape.
Open Show Options and tick Reverse Source shape from target. Add Smoothing Moderator and Content Type if you want. Then click Accept.
Your garment should now be fitted to Genesis.
Then save as Support Asset/Dsf Figure or Prop