First thing you’ll do is apply here.
Then, while you’re setting up your account and waiting for approval, you’ll want to make sure your location is correct. Do NOT skip the part where you select your time zone.
Time doesn’t matter, but your location does because your ads are only shown to the locations you live in.
For instance, if you’re in the UK? The UK is one of the only options you’ll get for running ads to. You won’t get the US as an option. Or Canada.
On the flipside, if you like in the US, you’ll get the US and Canada, but forget about the UK, Europe in general or Australia.
I don’t know why this is the way it is, but it is this way.