to play online, it's fairly simple : just go in the "Training Club", then click on "Play", then select "Network Play". There, click on "Join Game", then "Find Internet games". Click on a game name to enter it. If no game is available at this moment, then click on "Create your own!" and at last "Create Game", and wait for an opponent to join your game. Statistics will show you approximately how long you have to wait.
If you have a router, you have to forward the port 4321.
If you have a firewall, you have to allow Tennis Elbow to access to Internet.
You can read the complete documentation here :
http://www.managames.com/tennis/doc/Ten ... ml#network
Else there's no way to play without pay, but check your email box...