// Update the Python version to match your project.
mkvirtualenv name_of_your_virtualenv --python=/usr/bin/python3.5.1
Name the virtualenv after your project, because the command to activate it has global scope (is that the way to describe it?), so you can't name all the virtualenvs "venv"; you'll have a name conflict.
(Tangent: You'll activate the virtualenv with "workon name_of_your_virtualenv")