This is how you would link an existing Job to an existing Sales Order.  normally this is handled automatically when you use the Order Job Wizard, but this is the manual process.

1. Open Job Entry, and select the Job you wish to change.  The Job cannot be Complete or Closed.
2. Look in the Demand Summary tab to see if there is already a Demand.  if so, you will have to delete the existing Demand to add a different one to the Job.
    
3. Use the File -> New -> New -> New Demand Link -> [Choose the appropriate type of Demand Link]
   1. Make To Stock - if this is a Stock order.  Fill in the Warehouse it will be stocked to, and the Quantity.
   2. Make to Order - if this is a Make Direct to a Sales Order.  Fill in the Sales Order, Line and Release information, and the Quantity.
   3. Make To Job - if this is a Make Direct to another Job Material. Fill in the Job Number, Assembly Seq, and Material Sequence, and the Quantity