First, from any Google-related page, (gmail, drive, search) click on the 9 - dot menu-thingy found in the upper-right as indicated by the orange arrow in the image below.
You are going to look for the Brain-Pop icon.
You may have to scroll a bit to find it. You may even have to scroll all the way to the bottom.
Click the BrainPop icon and select your account to sign in.
You should then be able to choose your BrainPop item and proceed.
