You can change your daily and weekly overtime rate by heading over to your company settings. Scroll down all the way to Human Ressources. There you will find the Overtime parameters.

Daily Overtime

If you pay your employees a different rate after a certain number of hours per day, you can specify the rate inside these boxes:

Weekly Overtime

If you pay your employees a different rate after a certain number of hours per week, you can specify the rate inside theses boxes: