If you have book credits, they will be applied automatically. Also, if your purchase exceeds the credits available, you'll be asked to complete the purchase using a credit card.
Note: Teacher book credits differ from School content credits. Teacher credits are only available to a single teacher. School content credits are available to all teachers rostered at that school. Admins can update which teachers have access to these credits.
If you have book credits available, you will see this icon
Hover over the icon to quickly check your book credit balance
Click on the book credit icon for a more detailed overview
Book credits will be automatically applied