To install flask web framework,you must install python and pip .
If you don't have, please check the below link to install python and pip
http://ampersandacademy.com/tutorials/java-2-python-installation/
http://ampersandacademy.com/tutorials/pip-python-package-index-installationwindows/
After installing python and pip execute the below command.
pip install Flask Thats all.
Reference: