In order to use these files you will have to prepare a folder in your evequest/uifiles directory.
To do this you will need to access your everquest folder (typically c:\program files\sony\everquest.) Then go to your uifiles directory and make a new folder.
I find it helps to name this folder for the character class your using it for but name it whatever you like. Then go into the directory default under uifiles and select all the files in the folder.
This is accomplished easily by going to edit and then hitting select all, then go back to edit and copy. Go back to the folder you made, go to edit and paste. You now have a folder ready to be moded.
Open the zip file of your choice and copy the files in it to the directory you created letting it overwrite anything it needs. Then when in everquest use the /loadskin command and select the folder you created and your skin is set.