When you hit B to select the jump game you see three empty circles at the top of the screen.
As soon as one turns black you have to press the corresponding button (A, B, or C) as quickly as poss (within 0.5 seconds). To win you have to press each of the 3 buttons within 0.5 seconds each time.
Check your Tama Instruction sheet - it gives you a brief outline of the game.
Best, etc.
TamaMum