SSH stands for Secure Shell. It's a method for connecting to remote places.
As a developer, you will need a SSH client in combination with a SSH key in order upload changes to Ubuntu source.
First, make sure you have install the SSH client:
$ sudo apt-get install openssh-client
Creating the SSH Key in a Terminal
To create a SSH key in a terminal:
$ ssh-keygen -t rsa
Read more about SSH at the Ubuntu Community Wiki