Really New and wondering

Ok im new to snooker, i have been down my local club to play and lets be honest im not even close to been a rough diamond, but i enjoy watching..

Anyway i play on the computer alot (please dont shoot me down) and i have a question regarding snookers..

If on the break you snooker your opponent , lets say behind the green ball and he misses 3 times to hit the red's is that a claim game ? at what point can you claim the game ?

Really New and wondering