to create a python virtual environment:

proj-directory> python -m pip install virtualenv

proj-directory> python -m venv flask

it creates an virtual environment named flask.

to open that environment:

proj-directory> flask\Scripts\activate

upon successful activation, it shows like this

(flask)proj-directory>

now install the required modules with their corresponding version using the command:

(flask)proj-directory> python -m pip install -r requirements.txt

finally to run the project, use:

(flask)proj-directory> python app.py

This will launch the app in localhost 5000 which is flasks default port

to close your virtual environment type:

(flask)proj-directory> deactivate

it terminates your virtual environment and that (flask) part is now gone