When you say you can't get clothing to fit are you using clothing designed for that particular figure to fit or are you trying to get clothing from one figure to fit another? If the former, do you understand the difference between conforming and dynamic clothing?

Conforming clothing is normally in characters in the library and is quite easy to use. Here is an example. Start with default scene with LaFemmme. Now go to the library and find girl gear, this should be in something like LaFemme/clothing/republishing/girl gear. Now drag and drop the pants and top onto the LaFemme figure. This will CONFORM the clothing to LaFemme. Now if you pose LaFemme the clothing should follow the figure. If it doesn't right click on the clothing and a menu will appear. One of the items should be "conform (clothing item name) to " select this and a list will appear, select LaFemme from it and everything should work.

If you are still having problems, or this wasn't the problem you were having just explain them.

And Rendo has plenty of tutorials on this site under community tutorials, you probably need to start at the oldest and work forward, although I haven't watched the second one about runtimes for a while but when I did I wasn't impressed with that one it's a bit out of date.