How can i use a port other than the ones listed?

So Im trying to add a port that is not listed on Cloudflare but the only insyructions I see is to grey out the proxy on a subdomain. I dont have a subdomain I only have a main domain. Does any one knwo how to add ports other than the ones specified?

Thank you in advance.

By subdomain, it means www, app, etc.
You can use an origin rule to forward the requests to different ports