Setting SDK for Garry's mod


I recently started thinking about mapping for Garry’s mod. I don’t really know how to configure it, and there’s lots of outdated tutorials on how to do it.
I tried most of these tutorials but they didn’t work as i expected.

Can anyone help me or give me a link for an updated one? Thanks.

EDIT: shit, is this the wrong section?

Just load CS:S, EP2 or whatever you want to use in hammer together.

This should help you out if you need any more help with it.