Does adding anything to your websites code, like hidden keywords

Completely agree with Stanley on this . The main method of using key words in content of your site being properly utilized is much more valuable than spending large amounts of time incorporating them into your site code as it can make the process drawn out and hectic.

I believe in some ways that yes, it does actually help with ranking to some extent. But I'm not sure how much it really helps. You're just as better suited to use keywords in your posts and content, as that would likely be the better alternative.