For people who are coming from windows or people who are uncomfortable with the command line, gufw is a gui for "ufw" The Uncomplicated FireWall. Gufw is described as: gufw is an easy and intuitive way to manage your Linux firewall. It supports
common tasks such as allowing or blocking pre-configured, common p2p, or
individual port(s), and many others!
It can be found in Main>System>Install/Remove Software.