To add a single account/user, you must be logged in as an Educator plus Admin. From the Manage page, select the Accounts tab. Then choose whether you want to create a School, Educator or Student account. Educators (without the Admin role) are only able to add new Students.
Next, enter the information for the new account and click the Save button.
To assign Educators to a Student account, you must first save the new account, then go back into it. A list of available Educators will then be visible.