If you're not connected to the internet, do so now.
Open XTerm.
Type
sudo gainroot
Now you have to be very, very careful as you are logged in as root. Type
apt-get install ssh
This will install OpenSSH and start the SSH server daemon.
Now it would be a good time to set a password for user "user"; as root, type
passwd user
It would also be a good idea to lock root's password (as you will use gainroot in the future). Type
passwd -l root
Now, you can ssh into your 770 by typing
ssh user@192.168.1.x
Or whatever the 770s IP address is. In the future you can start the SSH server by typing
/etc/init.d/sshd start