Depends on your oauth provider. If you wish to use the examples from the readme you do not need to anything - they work out of the box

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.