There are two parts to having SSH on your machine. The OpenSSH Server allows other clients to connect to you, the client allows you to connect to other SSH enabled machines.
Installing the OpenSSH Server
Install the OpenSSH Server package from the Ubuntu Universe – on the machine you want to connect to, type the following into Terminal:
sudo apt-get install openssh-server
If you can’t get out:
sudo ufw allow 22
Installing the OpenSSH Client