Hi there. I got steps that help you add a job to a customer in QuickBooks Desktop. 

Here’s how.

1. Go to the Customers tab.
2.  Select the Customer Center on the drop- down.
3. Right-click on your customer's name, then select Add Job.
4. Enter the necessary information, then click OK once done.

See the screenshot below for your reference. 

To add up, here are some links that you can visit about entering multiple jobs and pulling up reports that contain its details in QuickBooks Desktop for reference:

• Track job costs in QuickBooks Desktop.
• Customize customer, job, and sales reports.

If there's anything else that I can assist you with, let me know. I'd be happy to help. Have a lovely day!