where to create virtualenv 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: start virtualenv

source env/bin/activate

Example 3: create virtual env

python3 -m venv env