bitcoind – Apply SSL for RPC Port – Ubuntu Server 18.04 VPS

I run bitcoind 0.17 in a particular port of the Ubuntu 18.04 VPS server. I want to give the SSL certificate for the RPC port. I already know how to generate a self-signed certificate with OpenSSL. But I do not know how to apply SSL on a particular port. Please give an idea about this.

Also refer to the following link to apply SSL to the Apache Help.
https://bitcoin.org/en/release/v0.12.0#rpc-low-level-api-changes

But it does not work. I think it's an old document. All new documents are available to archive my target.

Thank you…