Best of the BestG 5

You need win a game over xbox live against 5 other human players.

There are 2 ways to do this.

1. Custom match
Host a match yourself.
* Press "Play Online"
* Press "Select Players"
* Press the "+" to invite friends or at the bottom "open for public", repeat this 5 times.
* Press "Invite - Proceed to lobby"
* Press "Go, start the game". You need to have at least one other player to join your game before you can press it. If you start the game before all players joined it will give you a warning that not all players you invited are there yet.

2. Quick match
* Press "Quick match"
* Select your number of players at the bottom by pressing on "+"
* Press "Start search"
* Wait until you are with six. Note: The host can start the game anytime, so this method is not guaranteed to be started with six players.

Warning: The servers are really bad, so you might not be able to connect to them. Just keep trying at another time and eventually it will work. The difficult part is to be with 6 online at the same time so you can start the game. Once it is started, you can play your tile when it is your turn. No need to be online at the same time anymore. It takes some time if you have to wait until the previous players made their moves before you can take yours. You know who is the next player, so you always can send them a message over xbox live saying it is his turn.
How to quit out? Press the back button and choose "Quit/Save".
How to find your games in progress? In the main menu on the left side, press "continue" and all your games in progress will load there. Press one to continue.

I doubt you find 6 players randomly. You probably have more luck to find enough people by making a gaming session.