Update installation.rst

docs/installation.rst

@@ -31,7 +31,7 @@ Get a copy of this code either by downloading the zip file from GitHub or
 
 Optional, but highly recommended, is to create a new `python virtual
 environment`_ if you're using python from python.org, or to create a new `conda
-environment`_ if you're using Anaconda. Then activate your environment. 
+environment`_ if you're using Anaconda. Make sure you configure your virtual environment to use Python 3.6 or greater. Then activate your environment. 
 
 .. _python virtual environment: https://docs.python.org/3/library/venv.html
 .. _conda environment: https://conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html