How to make my website secure?

I am trying to create a website with Flask. However, on the address bar, Chrome said that my website is not secure. What could I do to make it secure? I did use the flask_login library and save the hash password to the database.

Thank you

you need to force https. After that, if you are using your own domain (not, then you also need to generate a ssl cert and give it to us. See this help page about that, and also options to generate it for free using letsencrypt and zeroSSL