If you have not upgraded your GitHub Windows client to GitHub Desktop yet, I would certainly recommend doing so. The new client is much improved, and does include the ability to change which branch you are working in.
Having said that, you should be able to build the Engine from the Release branch in Visual Studio 2015. 4.9.2 does have the experimental support for VS 2015 (as long as you get the additional commits I listed above). If you switch to the Master branch, you should have an easier time building the Engine in VS 2015, but the Engine in the Master branch is potentially unstable.