right, you can go back to the cbp website
on the right side you'll see a box saying "retreive application", click there.
You'll need to enter your passport number, and if you have noted it down, the application number you were given when you did the ESTA
If you forget to write it down, you can still retreive it by providing your names, date of birth and country.
but just note the application number when you get the confirmation online, it will be easier when you're ready to print