Hi there Gemma!
To play Live Chess games with a friend, all you have to do is click the "Friends" tab, right-click on your friend's username and click "Challenge to a Game". There you can choose the time control, etc. Then you click the orange "Challenge" button (or something like that) and it'll send out the game request to your friend.
Hope this helps!
Kind friends,
I have long searched the web-site, but I could not find an option to invite a friend to join a game on-line (I am not referring to matches lasting days, but to "live chess").
Perhaps it is not possible? Is the selection of an adversary for "live chess" only random?
Many thanks to all of you,
Gemma