If you aren't using G Suite for Education, learn how to get more user accounts here.
You have 10,000 user licenses with a G Suite for Education account. You can request more accounts if you need them.
Before you request accounts
Check how many of your licenses you're currently using. In your Google Admin console, you can download a list of users.
Request more accounts
If you need more than 10,000 user accounts, contact G Suite support.
Add the accounts
After you get your new accounts, you need to add the users to your Google Admin console. For details, go to Options for adding users.