For me it worked just selecting in Settings > Project Interpreter the panda python interpreter (python.exe, not ppython.exe.).
If you wanna use ppython.exe you have to rename to something starting with "python" like pythonpanda.exe, since Pycharm only considers an interpreter something that starts with "python". Anyway, ppython and python are supposed to be the same.
EDIT
Another thing that can make it work, is using another python interpreter (the standard, virtualenv, whatever) and placing a path file in a folder within the PYTHONPATH.
In other words:
- Create a text file named panda3d.pth
- Write two lines
path\to\pandafolder
path\to\pandafolder\bin
- Save it in the site-packages of your python interpreter
- Configure Pycharm to use this interpreter