John Sterrett walks us through upgrading an RC of SQL Server 2016 to RTM:
Please read the release notes. There actually might be a few things you need to complete before upgrading to GA especially if you are using Stretch Databases.
Everyone, should validate if they need to apply KB 3138367. msvcr120.dll should be version 12.0.40649.5 or higher.
This is a nice walkthrough with a lot of screen shots, making it easy to follow.