Yes it automatically tells your friends whe nyou log in. Also you see when your friends are logged on, and alos get notified if they log on whe nyou are already on. HTH Not been doing it long myself but love it
you can change your status, so if you wanted to appear to be offline, or for it to say "away" or "busy" or whatever, you can do.
There's a drop down box at the top.
The mistake that I made when I first got it, was thinking that it was as much of a novelty to everyone else as it was to me. I kept IMing people just to say "HI" and I tended to get a bit upset when they changed their status to "busy" or responded with a terse "I'm busy, I'll get back to you"
YOu can also set it so that it comes on automatically as soon as you switch your computer on and go online.