Hi Eddy,
Since Experience Demo is built upon SRWorks Plugin and written not with C++ but with Blueprint, it's pretty normal that it only has one .cpp file of its own.
Have you added SRWorks Plugin into the Plugins folder? If not, try adding the folder SRWorks (from SRWorks SDK UE4 Plugin) into the Plugins folder of the demo project.
Cheers,
Renee