I tried to learn how to use Cloth setting to fit Boho dress to my nude Figure LF 2, and switched to what I assumed was a non-dynamic set T shirt and jeans, but when I try to dress LF 2 with it, it can't find her and instead goes to LF 2.1, who already wears shorts, whom I don't want to have it. have I somehow confused the id of LF 2, so the system thinks she's not present in the scene and only LF 2 1 is? 

First, check edit>preferences and make sure double click isn't set to replace.

If that's not the case, conforming clothing is usually in the figures tab of the library. If you've rearranged your library and combined the 2, there's a quick way to tell if your clothing is a conformer or a prop/ Look in the corner. A person means a conformer and a hat means a prop.

If the clothing is a conformer and it's conforming to the wrong person, you can select it and go to figure>conform to and select the correct figure. If you're dragging and dropping from the library, make sure you drop it on the correct figure. Watch for a yellow message that will tell you what figure you're going to drop it on.

If you just double-click on a conformer, you'll load it unconformed and it will load in the center of the scene. You'll need to conform it manually.

If it is another dynamic outfit, make sure you have the figure you want to wear it selected as a lot of dynamic clothing loads parented to the selected figure.

Also, don't forget to check the nudity box when you have a nude figure in the scene

red, the dress is conforming see shot, but when I try to conform it to LF2 I get no choice the popup box?

lf 2.1 is a different figger! 

don

The dress you're showing is a prop, hence the hat in the corner. Props aren't conforming. Since La Femme 2 isn't listed, you have her selected. The Marketplace page also states it's dynamic.