If they are in your friend list here, then when you are both in Live you can find them in the Friend's tab. Click their name and challenge.
If they are not in your friend list, then you can find them in the Games > Players. It is a littler hard to find them there but you can click on the first letter in their username at the bottom of that and scroll through.
You can also use chat commands to challenge people that are in live:
https://support.chess.com/customer/portal/articles/1444911
Sorry if already covered, but I have been looking all over...
How (If Possible??) can you play 'Live Chess' games against a chosen opponent. (Ex: A friend is online and you would like to play).
Every option I try or see directs to 'Online Chess'.
Whether it be a rematch from an old former game, or in my case, I have a young nephew trying to learn....I would be nice to figure this option out????
Thank you......