If your school has purchased an institutional account, you can register with ZenGengo as an institutional user.
First, navigate to https://www.zengengo.com and click on the "Sign Up" option:
Next, fill in the form and sign up with Google or Microsoft:
On the next page, click the "Upgrade" button in the top right corner of the site:
On the next page, input your institutional access code (available from your institutional manager) and click "Activate":
Click "OK" to confirm the institution you wish to join:
You now have access to the ZenGengo platform and you can start creating assignments.