At the top of the page, it says, Log In.
When you hover over Log In, there is a box that pops up.
At the bottom of that, there is a link to Register. Click that link.
The registration form will have you enter your name, email address, and create a password. Then it will ask you if you are registering as an employee or representative of a school or educational institution.
Click Yes, then a box will pop up asking for your zip code. Enter 60510. Several schools will populate with that zip code. You will choose INTERNATIONAL-DIGITAL ONLY at 770 N Raddant Road, Batavia, IL 60510. For me, it shows as the last entry.
It will then ask you for your role at the school. If you are going to be using one of the POGIL books, be sure to choose Teacher as the role. Do not choose Department Chair even if you are one. Enter a discipline (if there is one) and then click the thing to agree to Terms of Service and Create Account. Once that is done, go ahead and start the order for your POGIL books.