Use CasaOS as a web hosting server

How can I use CasaOS as a web hosting server?

I would not recommend this. CasaOS is designed for a home lab. Also, do not expose the CasaOS dashboard to the web. There’s nothing stopping you from putting it on a cloud server; people have done it; just IceWhale didn’t intend it to be used this way.

i just want to host my bio website in it

If you just want to expose one service, you can look at Cloudflare Tunnels.