Thanks. I accessed your account and confirmed your attempt to create Riley as a user failed so there is no Riley user. That's why she's not showing up as an option later in Step 83.

So based on another post of the same problem that I just saw, my guess is that you did the same thing when you were trying to create Riley as a user. Here's a screencap from the other case, showing the error message I suspect you saw:

As you can see. this person tried to give Riley the username "2@gmail.com" which is quite common and the error message is saying it has already been used by another Salesforce user so it can't be used again.

If you read Max's instructions carefully, you'll see they say to use your own username and just insert a "2" before the @ sign. The screencap in the instructions also illustrates this. So in your case, it would be whatever your username is with a 2 added in front of the @ sign and that would almost surely be never used before in Salesforce and the creation of the user Riley would work. Then she would appear later in Step 83.

So you just need to go back and do those steps again this time following super-carefully and you'll successfully create Riley as a user and she'll show up when you're in the later steps setting up the template, ok?