The key is to mark your source directory as a source root. Try the following:
- In the Project view, right-click on the Python source directory
- In the dialog menu select Mark Directory As > Source Root
The folder should now appear blue instead of beige, to indicate it is a Python source folder.
You can also configure this in PyCharm preferences by doing the following for a project that is already in PyCharm:
- In the Mac toolbar, select PyCharm > Preferences
- In the window that opens, select Project Structure from the menu pane on the left
- Select your project in the middle pane, if necessary
- Right-click on your Python source in the right pane and select Sources from the menu dialog