The first thing to do to get started with Octauthent is to setup Cloudflare on your site.
This is a step-by-step tutorial to help you in this task.
Once all your traffic is going through Cloudflare's network, you're just one step away from having password-protected pages on your site.
Follow this tutorial to get started with Octauthent
If your site is deployed on Vercel, this is the tutorial you need!