Hit the dropdown at the top of the page titled "Training & Resources," then choose "ProAdvisor Academy." Click the "Start Learning" green button.
Create an account.
You have to sign up for a package, but you have a free 30-day trial.
Once on the next page, hit the "Certifications" tab at the top, which will show you a list of options available. Choose QuickBooks Online Certification Level 1 to start with.