After Eyetest.com's ophthalmologist issues you a prescription, you'll get an email saying it's ready along with a link to sign in to your Eyetest.com account where you'll be able to access the script.
From there, you'll just follow the link in the email (or visit http://www.eyetest.com/common/secure/login.asp) to log into Eyetest.com where you'll have the option to click "download" or "print." Once you have your prescription, you'll be able to use it wherever you want to buy your contacts or eyeglasses. (And did we mention you get to do all that from the comfort of your home? Yeah: You do.)