how to transfer download game from itune store to ipad2

Connect the iPad to yoru computer and select the iPad on the left-hand side of your computer's iTunes, and on the right-hand side there should be a series of tabs, one of which should be Apps - select that tab, select that app, and sync it to the iPad.

Syncing apps : http://support.apple.com/kb/HT1977

You should also be able to re-download it for free directly on the iPad via the Purchased tab in the App Store app.