Bats are good animals to have around, why do you want to kill it?
How do you kill a bat?
Why would you want to kill it .. Bats are GOOD to have around.
In many places it is illegal to kill them. If you need to get rid of one call you local wild management department, and they can either help you or they can tell you who to call.
You don't. I hope you won't even try to do so, because not only is it inhumane, but there's a huge chance you'll get hurt.
If a bat is bothering you inside your building, you can find where it entered - and seal that place. If you generally want to keep them away from your property, try mothballs as the smell is repelling to them.