I finish a game and I want distribute it, what I need?

The same way as you build for Windows. You just need to change the build platform and it should be fine. Still, I strongly suggesting you to test it on the specified platform.

From FAQ

Are there royalties or a per-title fee?

No, Unity does not charge on a per title basis and you do not pay royalties or pay revenue share, even for games and applications made with the free version.

Can we sell games and make money with the free version of Unity?

Yes you can create and sell a game with the free version of Unity, without paying royalties or any revenue share. However, the free version of Unity may not be licensed by a commercial entity with annual gross revenues (based on fiscal year) in excess of US$100,000, or by an educational, non-profit or government entity with an annual budget of over US$100,000.

Please also be aware that the feature set of the free version is not intended for the production of professional games and interactive content. Lastly, games made with our Pro trial licenses may not be distributed nor used for commercial purposes.

If you to submit game to a specific platform check their Terms and Conditions of Use. These links may help you : https://support.steampowered.com/kb_article.php?ref=1657-WHKN-6841

https://developer.apple.com/library/ios/documentation/IDEs/Conceptual/AppDistributionGuide/SubmittingYourApp/SubmittingYourApp.html

Most of them take around 30% of the profit by the way

Edit : If you want to make money with your game and want to be really safe, you need to declare your revenue to your government.