How to set up a controller for Dota 2 - tutorial 17/12/21 

Dota 2 got a new feature, you can now use a controller with full support. It's a little buggy sometimes, but you know, it's early access, so it's basically perfect in the future.
I failed to set it up yesterday and succeeded today.
Here's how you set it up as of 17/12/21.