I'm going to try and show as much detail as feasible here, for those of you that are barely computer literate. Here goes: Now if you don't know how to move about your directories in Windows you better have someone that does help you. You also should understand how to unpack a file.
1. Download the UI Files you want, remember where you save them. (I saved mine in c:\program files\everquest\uifiles.)
2. Get into your \uifiles directory as shown:
3. Add a new folder/directory called whatever you like (eugee in
this example) 
4. Next unzip the UI files you wish to install into this new
directory. 
5. Now log into EQ and type "/loadskin eugee
1". Obviously if you don't call the folder eugee use the name you
used. The 1 on the end ensures that your window positions and shading will
not be tamperd with.
6. Tada! This is what the finished product should look
like! You'll notice my action window is open and resized, that's where the
maps are.
That's all there is to it, UIs install much easier than they used to now!