Hello, @keerthidl

Speaking of DNS you can point a subdomain name to a single IP address (point the subdomain to the IP address of your droplet).

You can use multple subdomains (and host multiple websites as well) on a single droplet. You just need to configure the Virtual Hosts for the subdomains in the web server (Apache, Nginx) configuration files.

You can check out tutorial on how to set up a node.js application on Ubuntu 18.04

https://www.digitalocean.com/community/tutorials/how-to-set-up-a-node-js-application-for-production-on-ubuntu-18-04

Prerequisites

This guide assumes that you have the following:

An Ubuntu 18.04 server setup, as described in the initial server setup guide for Ubuntu 18.04. You should have a non-root user with sudo privileges and an active firewall.

A domain name pointed at your server’s public IP. This tutorial will use the domain name example.com throughout.

Nginx installed, as covered in How To Install Nginx on Ubuntu 18.04.

Nginx configured with SSL using Let’s Encrypt certificates. How To Secure Nginx with Let’s Encrypt on Ubuntu 18.04 will walk you through the process.

Hope this helps!

Regards,
Alex