First up you'll need to create a service for your Labor charges under Services in your Inventory.

Select 'General Services'

Enter in the Service information (you can also select the pricing structure - flat rate, percent of order, etc)

Most vendors create a new Line Item Group called 'Services' in their projects where they would include all of the services for that project, but you could just as easily add a Labor Service in the same Line Item Group as a Tent to show both your team and your client what the labor is being used for.