You need to download Visual Studio 2015, also the source code to UE4, which is done one of two ways and with slightly different outcomes. If from Epic Launcher> Library you link on Grab the source on Git Hub, you can either download the files, which you can then make changes to the engine in VS 2015, or the preferred route, use Git Hub to make a branch of the engine on your machine, the advantage here being that whatever modifications you make can a) be shared with the community, and b) make it easy to keep that modified engine up to date against UE4. I recently had some help with the latter, and when I get back to town I’ll see if I can’t just make the code that worked for me available to the community, will post an update here.
As for how you use Git Hub or go the other route, you’ll need to through the instructions in that Launcher link or have others help you over the forum. It’s been too long since I’ve dealt with the simpler download route, and then more recently I had a friend walk me through setting up Git Hub, not so complicated, but I’m not the one to help with that.
As for the code, why don’t you first get the UnrealEngine.ini going in VS 2015, and by the time that’s done, I’ll be back with help on the code.