Where do I put the hot wire on a double pole 20 amp breaker I have a 12/2 wire I have a black and white wire I need to know does the black go on top or bottom because there is 2 screws on the braker thanks
What are you trying to accomplish?
A double pole breaker is used to supply either a 120/240V circuit, a straight 240V circuit, or a 120V multi-wire branch circuit.
If you're wiring a 240V circuit, the black wire goes to one terminal and the white goes to the other. If you're trying to wire a 120/240V circuit, or a multi-wire branch circuit, you'll need another wire. If you're trying to wire a 120V circuit, you need a single pole breaker not a double pole.
Both terminals on a double pole breaker are hot.
It doesn't matter unless you want to follow a color convention that typically isn't used in residential work; primarily because most of the wire is cable assemblies and not 12/3 where you'd have a red wire as well.
The color convention I speak of is Black-Red (Black-Red-Blue for 3-phase). This means as you go down from the top and both sides of breakers in the panel alternate in color.
1 Black 2
3 Red 4
5 Black 6
. . .
A 2-pole breaker spans two colors. Depending on where it's at, the "proper" way could be top or bottom. But like I said, it doesn't matter in terms of delivering power or for code.