Hi braekbot
Once your build of UE Source is complete. The executable for the editor is located here:
C:[Unreal Srouce]\Engine\Binaries\Win64\UE4Editor.exe
You can create a shortcut to your desktop or something.
I also recommend you running:
C:[Unreal Srouce]\Engine\Binaries\Win64\UnrealVersionSelector.exe
This will register your build so you can access the build from the “Select Version” menu when you right click a .uproject file.
Hope this helps.
Good luck!
Alex