In the v2 bump game: The screen will come on, and two characters will appear (yours and a random one) it'll play music than it will say "PUSH!" and then you push button B really fast, than press it again to stop it, how ever much power you got will depend on whether you win or lose. (There's actually a bit of randomness in it I think, because I've gotten a full bar and still lost. many times!)
But this should all be in the instructions, maybe you should read them?