Wow, I think we've really confused you. Your half cloth and half conforming and we've made a mess.

OK, conforming and cloth sim are completely different animals and are not related at all.

In a conforming clothing figure your build a model with body parts similar to the ones in the base figure, set up the joint parameters so the clothes bend the same as the target figure... Well this isn't the place for that full tut which is here:
Conforming Clothes
PhilC has an excellent tut on creating conforming figures too.

I think what may be easier, at least at first is to do a Dynamic Cloth. You have already imported the OBJ for the top you are half way there. The cloth sim needs a solid mesh so you don't need to worry about grouping stuff, well not as much any way.

With your bikini model loaded just drag it to position so all the bits that are supposed to be covered are. Now go to the cloth room. From here follow my cloth tut. (It's a click by click tut with lots of pictures :-) )

Cloth Tut Now, there are some issues with using conforming figure models in the cloth room. You may need to use the group tool to select just the polygons that are on the outside of the model and "Spawn" a new prop then use that for your sim. Once again PhilC has doing this covered.