http://www.eq2interface.com/forums/faq.php?faq=howto_install#faq_new_faq_item

Currently the interface command /loadui works in a sense it loads the custom interface but if you use it your interface will not work correctly. So here are the steps to use for now to load a custom interface and have it work.

Current Install Steps:

   1. Download the interface you wish to use
   2. Make a new folder with any name BUT with no spaces or special charaters (example: bobsui) in the UI folder that is inside your Everquest II directory.
   3. Unzip the xml, dds, tga (dds,tga's must be in a images sub-folder) files into your newely created folder. Please make sure you dont have a folder inside of a folder when you do this. %\Everquest II\UI\bobsui\jillsui\*.xml (wrong) | %\Everquest II\UI\bobsui\*.xml (correct)
   4. If you are going to use multiple interface peices just unzip all of them into the same folder.
   5. Go back to your Everquest II directory and create a new text file and put the following code inside of it:
      Code:

      cl_ui_skinname bobsui cl_ui_subdir UI/

   6. Save the file as eq2.ini (make sure you dont save it as eq2.txt or eq2.ini.txt)
   7. Load up Everquest II and your new interface should be working.

Once they fix the /loadui command using custom interfaces will be ALOT easier and these steps will be updated.