In previous versions, setting up provisioning profiles was done manually. You generate distribution profile, download it and then distribute your app. This had to be done for every development machine which was extremely time consuming. However, in most situations nowadays, Xcode 8 will do most of this work for you. Make sure you sign in with the account which will be used for distributing the app and then simply select “Automatically manage code signing” in Targets -> General.

https://i.stack.imgur.com/rZgjJ.png