PyCharm cannot find mpl_toolkits

I am running the latest community edition on a Mac OSX.  I need to use mpl_toolkits (mplot3d specifically).  PyCharm seems to know nothing about it:

>>> import matplotlib.pyplot as plt
Backend MacOSX is interactive backend. Turning interactive mode on.
>>> from mpl_toolkits.mplot3d import Axes3D
Traceback (most recent call last):
File "<input>", line 1, in <module>
File "/Applications/PyCharm CE.app/Contents/helpers/pydev/_pydev_bundle/pydev_import_hook.py", line 20, in do_import
module = self._system_import(name, *args, **kwargs)
ImportError: No module named mpl_toolkits.mplot3d

I used the PyCharm package manager to make sure I have the latest version of matplotlib, so mpl_toolkits should be there.  Any idea how to get access to mpl_toolkits?