Not much point in seeing the C++ Classes in the editor, you can't edit them from the UE editor, it would open Visual Studio if you wanted to make changes.

Better to just open the project in VS, if you are installing it just now, or haven't done this step yet, you will need these plugins so everything works without a hitch.

Then you build for Development editor in VS, after that you can open UE editor and you should be able to use what you made in C++