9v dc and battery connection help please

[Kipper4]

I've made an amp that requires 9v dc power and i want to be able to use battery or walwart.
How do i wire the walwart plug and battery terminal so that if i use the walwart the battery is isolated?
Thanks for any help you can give

[haveyouseenhim]

The unused tab on this picture is where you connect the battery positive. When a wallwart is plugged in it switches away from the battery