When you see a file with a smiley icon, right-click it & choose chat. Then type in what you want to say to them & press Send. Here's some more clues with images:
http://www.gnutellaforums.com/showth...threadid=31572 How do you receive a chat message in Limewire?
http://www.gnutellaforums.com/showth...threadid=33584 chat setting up