In case anyone else goes looking. There might be better or more appropriate settings but this is how I got it working with on pyCharm Pro. Also, since wsgi.py has the default config file hardcoded, it doesn't seem to typically matter that you aren't passing it in through the pycharm run/debug configuration.
Edit Configurations... > + > Flask Server
Target Type: Script path
Target: <path to>\flaskbb\wsgi.py
Working Directory: <path to>\flaskbb\ (so the top level folder, not the source folder, that creates import errors associated with modules named 'email')