You play jump by pressing the relevant button when the circles light up on the screen. For example, you hit A when the first button lights up. B for the second, and C for the third.
You need to press the button in 0.5 seconds though, so be quick! You can win up to 100 points.
Bump is quite hard, it helps to beef your tamagotchi up by feeding it LOADS of snacks before you play. I've actually given my tama quite a few toothaches by doing this
. Playing a lot of games will bring it's weight back down, so don't worry.
Press B when the screen says "PUSH!". Then press B again when the bar is at it's highest point - this indicates your power. It works best for me if I don't even look at the bar, and just press it randomly.
Your tamagotchi's will push against eachother, and if you manage to push the other tama over, you win! I've only been able to get up to round 6, though.