If you have been using TD Basic but would like to add great features like Student Dashboard, you will need to upgrade your subscription from within the Teacher Dashboard application.
As an admin of Teacher Dashboard, click on the Admin menu link and go to the subscription tab.
From here you will see two options:
Scroll to the bottom of the TD Plus option box and click on the 'Pick me!' button
You will see a popup where you need to enter your billing details. Click on 'continue' and you will be upgraded to TD Plus. You will receive an invoice via email shortly after signing up.