Autocompletion doesn't list a majority of functions, etc.

Hello, I have downloaded and set up a pre-built library for Windows (here) according to the README. Most importantly, I have set the PYTHONPATH environment variable to the specified path. When I import and use this library, PyCharm does not autocomplete a majority of functions, etc, which is odd because the Python IDLE does. Both are using the same Python Interpreter. I have tried the suggestions under Pycharm Code Completion - Troubleshooting to no avail. How do I fix this?