Find out the TX2 IP address by running:
From your own computer:
username will be the one you create when booting up the Jetson TX2. Then it will ask for your password, also the one you just created. After entering your password you are in.
If you don't want to bother with passwords, add your local computer public key to the TX2 by running:
ssh firstname.lastname@example.org again, and you should get straight into your TX2.