What should I do to keep my website server on even though my computer is off?

I clicked 'connect using SSH' button and after that, I typed python manage.py runserver 0:8000. I expected the website to be accessible all the time when I just type that once, but if I don't keep my computer on and press refresh button every 30 seconds, I can't access the site. I should type same sentences every time to keep my site accessible. What should I do to keep my website server on even though my computer is off? I'm a student and not a professional so I'm expecting kind and easy answers. Thank you.