I was having a problem finding files, but I figured out how to access and get source files, I just haven’t aded c++ source files to my profject from editor yet (mainly because I don’t know how), if I rightclick on .uproject file in it’s folder, I get option to generate visual studio project files. I am not sure how to add c++ source files to project yet but I’ll figure it out.
Are you attempting to add new files using visual studio or editor. Or are you attempting to integrate files that weren’t apart of your project?
If you are attempting to integrate files make sure, if they are game files, that they are situated below your '\GAMENAME\Source\GAMENAME' folder. For example if my project is called MyAwesomeGame. new game files would need to be in c:\MyAwesomeGame\Source\MyAwesomeGame\NewCode.cpp
Make sure to generate project files after doing so.
If you are attempting to integrate engine or editor level code I don’t know where you’d be able to put them. Someone else here ought to be able to help you with that.