you create a physical prototype and present it to a publisher. i suggest you read "Game Design Workshop, Second Edition: A Playcentric Approach to Creating Innovative Games" by Tracy Fullerton if...
Well, there are alot of way. Either by creating a new Game from Scratch, by coding etc. but this is only for very skilled Coder.The best way to make your own game is by using a 'MAKER'just google it
Making video games can be complicated and confusing, but if ur willing 2 commit, the rest is easy. Just go to Yoyogames.com and download Gamemaker. If you get the free version you can make 2-D games...