You may need the lockdown browser for AP testing, this guide will show you where to find the application.
Before you sign-in, on the login screen look to the bottom left corner.
You should see a button that says "Apps", click this and a list of applications should appear.
In this list of applications select the lockdown browser. Please note that this may be listed as "2021 Digital AP Exams".
Follow the on screen instructions to begin your test.