In one sentence, describe what the following article is about:

Once purchased, the extras must be activated to take effect during your game. They are available under the Extras section of the Start Menu. Once activated, they will remain active until you deactivate them or until you exit the game. Extras can be used in the cantina, story mode, free play, character bonus missions and mini kit bonus missions.  Extras cannot be used in super story, LEGO City or bounty hunter challenges. Some extras can be used in character bonus missions or mini-kit bonus missions.
Activate power bricks.