How to play multiplayer games on Android devices?

htcdesireedd

I have a HTC DESIRE have fifa 2010 and Carrom3D Pro which have multiplayer network build in im trying to connect it to another htc desire to play network games but with no luck, is there any setup i have to do to play, does it connect directly over wireless to another handset? do i have to be on a wifi modem to work ?... Im new in this so plz help me.