Download Etherpad: https://www.turnkeylinux.org/etherpad
After installation, you’ll need to edit nginx nodejs configuration file.
It’s located at /etc/nginx/sites-enabled/nodejs
Add the highlighted lines to your config file.
Follow “Create the Password File Using the OpenSSL Utilities” section to create your htpasswd file.https://www.digitalocean.com/community/tutorials/how-to-set-up-password-authentication-with-nginx-on-ubuntu-14-04
Restart nginx after creating htpasswd file.
Port 443 is port forwarded from WAN to NAT. Port 80 can be disabled if needed.
(This post is for documentation purposes since I was trying to solve my problem. if it helps you out, good)