1. Download the iPad version from the App Store (search "Syntorial")
2. Open the app, and create a new user.
3. From the Menu at the top left, select "Already Purchased? Log in..." and log in with your syntorial.com credentials. 

Additional Notes

1. Be sure to download the entire Essentials lessons in case you're going to be offline. Just go into the Menu at the top left and select the Download option
2. If you'd like to sync your progress between your iPad and computer, see How do I sync my progress between devices?.