Hmm, that’s a tough one, I’m sure there are some people out there that could help you, but what’s your plan for the game, would it use any store API (like steam, google play, app store), because each one would handle it differently, but would do it for you. As for doing it on your own, I don’t really know how to do the whole thing, I would just make it access a website and check for some number you posted in a page and check against the current one (user’s). If it’s higher, then popup a message with a link for the update.