Welcome to the Community, timdorey.
You can purchase a payroll license for QuickBooks Desktop by visiting this link. From there you can choose different types of payroll subscription that suits your business needs.
Once done, you can have this article as your reference on how to activate payroll services: Activate QuickBooks Desktop payroll services.
Additionally, here is an article to become more familiar with how payroll works in QBDT:
I'll be right here if you have other payroll questions. Keep safe and have a good one.