Where do I go on the website to do the walker certification?

Walker certification is not an online function it is a test done face to face with a Rover employee I suggest you contact Rover Support for further instruction @ [Edit: Rover’s contact options have changed. Visit the Rover Help Center at https://support.rover.com/ to find the phone number, help articles, or chat with the team]

So after a lot of digging through this site I called Rover Support 9:28 pm est. Rep didn't sound too sure about it and said she would leave a note on my account for that department to reach out SO sounds like it's still very much in a nascient stage.

You won't find much upfront info on how to complete the certification on the website. Assuming your area offers the program and you signed up for RoverNow (call Rover support [Edit: Rover’s contact options have changed. Visit the Rover Help Center at https://support.rover.com/ to find the phone number, help articles, or chat with the team] if you aren't sure), you'll receive an e-mail with a link to the certification training. There is a lot of info, quizzes and videos. One of the last parts of the certification is a collar & harness test in person - if you aren't familiar with some of them, don't worry. Be sure to watch all the harness training videos as they are very thorough and informative. I didn't know several of the collars/harnesses but having reviewed the videos, I did great on my in-person test. Throughout the process, Rover is great about sending e-mails and texts to keep you on track.