At the very simplest level of Time and Materials markups, you can just say you want to mark up labour at a certain percentage. To do this, navigate to the job entry screen. Select item [e] Job Costing on the navigation panel, and under that heading, select item [a] for Job Entry:

When you select Job Entry, a window will display that lists all your current jobs:

As with all the entry screens, you can use the fields at the top of the screen to filter the list of jobs. Select the job you wish to set up billing for. In the Accounts Receivable section, enter the labour markup:

In this example, Abio will markup all timesheets posted to Job 1 by 10%.