The very first thing you want to do when you first enter the Heroes room at the Zone is to get your tables oriented as a list, so you can see what games are looking for people.
First, click LIST VIEW, from the toolbar toward the top of the page. Then, click the column BETWEEN the INFO and GAME NAME columns. This will bring all the games looking for players to the top of the list, games which have already started will be at the bottom.
From there, you can scan the list to see who is looking for players. Look for players in same tournaments as yourself, with similar playing preferences, the host will usually include this information in the game name, or in the description, which you can read by clicking on INFO.
If you see a game you like, as the host in lobby if he/she would like to play, or send them a Zone Message asking same.
You can also host a game, by clicking QUICK HOST. Then you can click SETTINGS to set up a game name (a good place to put whatever tournament you're playing in), and description, where you might indicate preferences about maps, templates, or rules.
You may also select a password. You'll find that tournament players always use passwords to keep newbies from jumping into their games.
Remember, though, today's newbie could be tomorrows opponent, always treat other players courteously and with respect.