How do you use extra on Lego batman

if u have a Nintendo ds then this is what to do:
press start that go to extras then if it says NO EXTRAS BOUGHT! then u have to buy some. If its a list with NO beside it go to that extra then press A u will see that its turned to YES now. All the extras can be activated at once. NOTE: THAT U HAVE TO ACTIVATE THE EXTRAS EVERY TIME U PLAY!