Review the notice at the top of the screenshot:

The message seems a little confusing because we call the thing you log in with as a User Center account but we're telling you to create a User Center account.
In reality, your account needs to be associated with a "customer."
This can be done one of two ways:
- An existing customer adds you to their User Center account (useful for consultants and the like)
- Create a new Customer, which you do by clicking on that Create Your First Account link
Fill in the details:

After you hit submit, you will be associated with a new "customer" and will be able to generate evaluation licenses.
I will add this to the How to Request an Evaluation License doc I created.