A friend and I both have Medal of Honor for the PS3. We want to play against each other in online multiplayer mode, but we don't know how. Do you know if it is possible?
Just connect to PSN (PlayStation Network). You can do this either wirelessly with newer models, or with an ethernet cable.
Once you've connected, create a PSN account. Then, insert the game disc.
Go to Multiplayer and scroll down to play with friends. You'll have to get your friend's user name and add it to your friends list. Then, select the friend there.