Follow these steps.
1. Go into this: http://steamcommunity.com/greenlight/ and when you are on it, you see this:
2. Then you gonna click on "Submit your product" here:
3. If you can't see it, here: http://steamcommunity.com/workshop/editgame/?appid=765
4. When you are there click on "Submit Concept", http://i.imgur.com/jrkHOQQ.png
5. When you are there, http://i.imgur.com/oRGtnq4.png
6. When you are going to publish and things, you write in the name of the game (you must be the owner of the game, do NOT copy others).
And this Guide was just about how to come to it, and things like that.
Have a great time :)