Karros Canyon is a capture-the-flag game.
Click the battlefield button and click Karros Canyon to register for it. The game will notify you as soon as there are enough players. You can also join the game as a group of 3 people. For that register as group in the battlefield tab.
After entering the game you will find yourself in either the red or blue team. Goal of the game is to capture the flags, kill enemies before they take your flags and reach 3,000 points before the time runs out. One game is maximal 20 Minutes.