Hi Kathryn,
Are you referring to the Learn About series in your Learning Resources? If so, you can access those by clicking:
Learning > Learning Resources> My Professional Development> Certificates
From there, you can see the list of Learn Abouts per age group. I am attaching screenshots for your reference as well. Once you complete the Learn Abouts per age group, a button at the bottom will appear for you to download your certificate.
Let me know if you have any questions! If you need additional assistance, please don't hesitate to contact our Customer Support team.