Vegitha, sorry for the late comment. You probably didn't add it to the right file.
"This goes in the popup tab under the nick-list file.(View - nick list once you're in the script editor)"
The only thing I can think of that would cause this is you forgot to click View-'nick list' in the script editor. You shouldn't put this in a separate file and load it. It has to be in the default mirc 'nick list' file under the popup tab.