how to create a new virtualenv

$ pyenv virtualenv 2.7.16 apps2
$ pyenv virtualenv 3.7.4 apps3

source env/bin/activate

             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)

virtualenv mypython