I would like to know how also. If you are the creator, do you host the game at your own server? How do you earn from contributing the game?
Make the app of the game and to make it go viral , make a page for it too.. Now , ask people to join that page and then go to that application .... thats just only.. But you should have designed the game in flash.
A very simple system is Instant FB Games: warriorplus.com/wso/view/33400. This isn't going to allow you to create the new Zynga competitor, but it should get you started. I you're looking for something more advanced and own a Mac you can get a "game engine" like gamesalad.com. Good luck... it's a long and tough road, but you can make A LOT of money.