First, look for an email from "Duolingo English Test" (englishtest-noreply@duolingo.com) with the subject "SYE Prospective Students has invited you to take the Duolingo English Test for free!"
Next, open the email. It will look something like this:
Click the "accept" button.
Next, you will need to log into your Duolingo English Test account (or create an account).
Once you are logged in, navigate to "Purchase a test." Your screen will look something like this:
Then, click "Checkout." A box will appear asking if you'd like to use SYE's coupon. It will look something like this:
Click "use coupon." Your screen will then look like this:
When you are ready to take your test, you will click on the "Get set up" button.