Usually its a 2 part process of 1) whitelisting the callback url in the oauth settings of the provider and 2) passing that whitelisted callback url in the auth flows
Unfortunately Oauth 2.0 is not a standard. It's a toolkit for making standards and pretty much every sufficiently large corporation is going to implement their own unique form. There is no one size fits all solution.
I assume you meant it is not a protocol, which surely is stated in oauth.net [1]. Still it is a pretty much a standard though.