Welcome to the Forum!!! :D
Oh, and it's spelled Betta. With 2 T's.
Since you're going to prepare for your Betta, the minimum for the size of your tank is 2.5 gallons. Unless you want to deal with ALOT of water changes.
Oh, and you also need a heater. They are Tropical Fish.
I'm sorry for telling you too much. It's just that, isn't it bad enough that Betta Fish are kept in Poo-Filled, Disgusting, Pint-Sized Cups?
Anyway, Good Luck with your New Betta!!!