title: PyCharm and external libraries
body: <p>I have started to use PyCharm IDE, but I was not able to determine how to manage external libraries there. For instance, PyCharm does not see <code>matplotlib</code>. In PyCharm's file manager, I clearly see the list of external libraries and there is no <code>matplotlib</code>. However, I have it installed and I know its location. </p>
  
  <p>How can I add this library to PyCharm environment?</p>