ranger,
If this friend is officially a chess.com friend in your Friends list, then when you open Live Chess - and your friend is in Live Chess too - you will see your friend's name in the list of names that appear under the Friends tab. If you want to play that person, just click the green Play link and you will be able to challenge that friend.
Alternatively, if your friend speaks up in Live Chess Main Hall (or any other chat room), you can click on that name and Challenge to a Game, as well.
There are other ways, but those are the two easiest.
Good luck.
How can I played with a friend already logged in live chess.
Thanks for the attention