HTTP is an unencrypted protocol. It's not secure. A lot of websites offer a way to fix that using Let's Encrypt to set up you HTTPS stuff.
Several webhosting providers have instructions for setting up HTTPS or HTTP/2 on their server.
- Netlify
- Dreamhost
- DigitalOcean
- via LearnWithJason (Caution: Written in 2016! Instructions and technologies may have changed since then!)