How to set up SSL cert for new port on Ex2 Ultra?

I’ve got a filebrowser server running on a different port than the main dashboard and I’ve got this port forwarded through my router for public access. I’ve got a public domain pointed at my public IP for access. I’m trying to secure this with SSL.

I know that in some cases I can use letsencrypt / certbot to manage this but I’m not sure how I would do that in this case, let alone install it. Does anyone know how I can manage this?

Greetings,

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