someone just contacted me who i was downloading songs of how do i do this?

You have to have chat enable as does the host you are try to chat with.

You can Highlight the host and right mouse click and select chat with host.

Just a note the host must be in front of the screen to respond. Most start a d/l and go on to others things, so they usually don't respond.

See How to Direct Connect, Browse & Chat (click on link)