I have venv folder but how to access to venv? code example

Example 1: how to create a new virtualenv

to make a new virtualenv: 
virtualenv env_name

             to activate this virtual environment:
source env_name/bin/activate (on mac and linux)
source env_name/Scripts/activate (on windows)

Example 2: python virtual env

$ virtualenv -p /usr/bin/python2.7 venv