To access Grammarly Premium, set up a personal account using your ECAE email address.
Note: Grammarly Premium is free for ECAE Users.
How to Switch from a Basic (Free) to a Premium Account (with ECAE email address)
If you ever registered at https://grammarly.com (Basic) instead of https://grammarly.com/edu (Premium), you need to log out by going to https://app.grammarly.com/ and clicking Log out in the left-side panel, then log in at https://www.grammarly.com/enterprise/signin. Next, find the email "ACTION REQUIRED: Confirm your email" in your inbox and click Verify email.
Alternatively, you can delete the Basic account you created by following the instructions described here. After that, go to https://www.grammarly.com/enterprise/signup to create a new account.