To install it, simply double-click (run) the theme file, it will install itself with malu.
If this fails (can fail in Vista without an admin account) place the file inside /program files/Mal Updater/Themes
Note: if you have older themes inside subfolders, you can delete them.

Vista Users: if you have UAC enabled or use a non-admin account, you need to have MalU closed to install a theme automatically