apt-get install python3-venv //if you don't have python3-venv
export FLASK_ENV=development
export FLASK_APP=application.py
python3 -m venv venv
. venv/bin/activate
pip install -r requirements.txt
python3 -m flask run
or
python3 -m flask run --host=0.0.0.0
Open at http://0.0.0.0:5000/ and see the magic happen