These instructions will work on any FreeBSD install, but you don't necessarily need nano to accomplish it. On a jail on FreeNAS you need nano because the keyboard combinations required to edit the config files cannot be executed on the web gui console.
Make sure root password is set:
passwd
Update pkg database:
pkg update
Install nano text editor:
pkg install nano
Open ssh daemon config file with nano:
nano /etc/ssh/sshd_config
You can ctrl + shift + w to find text
Un-hash and edit the following values:
ctrl + shift + x to exit nano
Press Y to save changes
Press Enter to confirm write
Enable the SSH daemon:
sysrc sshd_enable=yes
Start SSH daemon:
service sshd start