That has to do with the sender's end... they're asking you to use type in that command (in any mIRC window) in order to connect to whatever you're trying to connect to. I've seen some people come up with the same question regarding dcc sessions. It has also been suggested (can't remember where) to type /mode yournick -x
FYI, bear in mind that mIRC is NOT a file-sharing program (though it does have dcc capabilities...)
