I did some further digging (with the help of Google) and learned that you need to browse to www.TalentSmart.com/test to access the appraisal. Click on the "I'M READY" button, then sign in using your unique access code that was emailed to you by Amazon. I just tried this and it works.
You can enter your passcode to access the test at TalentSmart.com/test
As for the iPad, Apple refuses to issue passcodes for digital books like Amazon does for the Kindle. If you buy the book for the iPad you need to contact TalentSmart and you'll be given a passcode once you submit proof of purchase. You can reach TalentSmart at 888 818 7627
Thanks to Richard L. Parks for starting this thread and for you others who helped with answers. I bought the Kindle version of the book. Overall, the instructions on how to get the access code (I'd received it but not noticed it in my email) and use it were not clear. This thread gave me the info I needed. Thanks!