how to chat
 

i click to chat but it doesnt work, how do i fix this?

You need to have chat enabled. For windows that's Tools>Options>Chat & tick option & press apply button. For mac OSX you'll find it under Preferences>Chat.
More hints here: How to Direct Connect, Browse & Chat

In most cases they also need to have chat enabled (you can see if this is so by the smiley chat icon.)