Do I need Github source to rebuild engine?

I have engine version 4.7.3 installed. I did not explicitly choose to download the engine source, but I can see it in VS2013 when working on my C++ project. I have tried making modifications to the source and would like to build them, but running build on the engine project seems to do nothing. Do I need to explicitly download the source from Github to rebuild it, or am I doing something wrong? If I do need additional resources from Github, is it possible to download only the missing parts, or will I have to remove my current Unreal installation and start from scratch?

Hey shpen-

To make edits to the engine source code you will need to download from GitHub, however you do not need to remove your current installation. After downloading the zip file and building the engine you will be able to access both the source code version of the engine as well as the binaries version you’re currently using.