Rules are the same as in regular chess, the game is over when you checkmate your opponent.
If you did not checkmate your opponent (or vice versa), the person whose time has ran out(first), loses the game. The exception is if the winning side can not checkmate you by any possible series of legal moves(should the game continued), then it's a draw.
http://support.chess.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=680&nav=0,82
Looking at your stats, you're mostly playing a 30 min games, and time is not so important there. It gets more important with a shorter time controls.
I keeping playing and losing on time i cannot find where to read the rules help.