Combat isn't programmed yet, and will probably be the last big feature to be finished. Since this game is done by the players in their free time, this might also take a while ...
In the meantime there are always White Scenarios (see link at the top of forums ^), which are message-board based scenarios in which you can gain XP for roleplaying. Most of these scenarios allow combat, many are even based around it. However, none of the combat actually affects your character in the database, so you might be injured but you'll lose no HP. It's basically all for fun and roleplaying. (: