pip install %package_name%
The pip utility is included in Python 2 beginning with version 2.7.9, and in Python 3 beginning with version 3.4. If you are using an earlier version of Python, you need to install pip. For example, you can use the script https://bootstrap.pypa.io/get-pip.py.
For more information, see https://packaging.python.org/tutorials/installing-packages/.