Once you have created your individual task steps in the Task Builder you need to assign them to your Services.
To get started, go to Shopping Cart → Services
Once you're there, go to Manage
Scroll down to Add task and select from the tasks you have already created
Once you have added the tasks, you can either sort them out to the correct order by dragging
From now on, each time this Service is ordered the assigned Tasks will be added to the job.