Hi Kate,
you will find some additional details on the built-in whiteboard at the following link: home.pearsonvue.com/onvue/whiteboard
That also includes a tool to practice and get familiar with the online whiteboard, before the exam.
My experience with the online whiteboard was not great. I practiced using Paint (as the tool I linked was not available at the time), but my trackpad was not reacting promptly, so I rather preferred to practice using text boxes instead of drawing with my fingers. Not bad in the end, but of course much slower than paper and pencil.
Having no other choice, I just tried to practice, practice, practice, as much as I could—especially to find an effective way to "draw" a schedule network in a text box.
I'm sure you will find many more posts shared in this forum when searching for whiteboard and online/proctored exam.
Good luck on your exam!
Gabriella