Howtoforge published a tutorial about getting started with UFW (Uncomplicated Firewall) on Ubuntu 20.04.

Getting Started with UFW (Uncomplicated Firewall) on Ubuntu 20.04

UFW or Uncomplicated Firewall is an application to manage an iptables based firewall on Ubuntu. UFW is the default firewall configuration tool for Ubuntu Linux and provides a user-friendly way to configure the firewall, the UFW command is just like English language so the commands are easy to remember. 

Getting Started with UFW (Uncomplicated Firewall) on Ubuntu 20.04