In this tutorial we’re going to learn how to call the external file of css in html file. I have mentioned in very easy way so follow this tutorials.
First go to Project folder and create as per below
static/css/style.css
Next go to where you want to call this css file and put as per below code
<link rel="stylesheet" href="{{ url_for('static', filename='css/style.css') }}">
Now css calling successfully.