Access terminal and enter super user (sudo su).

Now enter the following to setup the tunnel:

ssh -D 8080 -C -N -i ~/path/to/privatekey.pem user@50.50.50.50

Open up Firefox and carry out these steps:

1. Menu > Preferences > Advanced > Network > Settings
2. Selet ‘Manual proxy configuration:’
3. Socks Host: 127.0.0.1 Port: 8080
4. OK

Check your IP using http://www.whatismyip.com/ to double check the tunnel is up and running.