There are two options available to input your school's license code dependent on whether you already have an account:
I already have a Peekapak account:
Sign into Peekapak with your teacher credentials.
Click 'Upgrade'.
Enter your license code and click 'Upgrade me!' to activate your account.
I don't have a Peekapak account
Visit www.peekapak.com/signup
Enter your details, including entering your license code.