User Pay Tab
Find the User Pay Tab
Go to More -> Users

Find your user and then double click on them or click the Ellipsis -> Modify

Go to the User Pay tab.

Select how this User will be paid: Hourly, Via Field Tickets, or Salary
For more information on setting up Rate of Pay and how it works see these two links:
1. Extensive Breakdown of everything related to the User Pay Tab including how it connects to Field Tickets: User Pay
2. Explains what a Rate of Pay is and how to apply them to technicians: Rate of Pay