# List available applications
$ ufw app list

# Output
Available applications:
  OpenSSH

# Allow OpenSSH
$ ufw allow OpenSSH

# Enable UFW
$ ufw enable

# Type "y" and press ENTER to proceed. You can see that SSH connections are still allowed by typing:
$ ufw status

# Output
Status: active

To                         Action      From
--                         ------      ----
OpenSSH                    ALLOW       Anywhere
OpenSSH (v6)               ALLOW       Anywhere (v6)