Well, first of all, you have to actually create the game. And unless you are planning on thinking very small and/or have a very good knowledge of computer game development and are a great artist, you need a developer crew. You also have to be ready to deal with common problems such as squashing bugs and patching glitches, and you have to get a legal copyright printed and signed unless you want your game to be stolen and be unable to do anything about it. You also have to be very careful of not copying other people, or else not only will you have angry players but angry developers which means you being sued. Submitting games is the easy part, see?
