Hi,
You can set up the required component in the inventory part/Part revision window/Product structure tab.

Then make the product structure status to ‘Build”.
Then once you create the purchase order line-->You can see the component automatically fetched to the “Components for Purchase Order Line” window
 

Does this pertain to a manufacturing shop order with outside operations or a purchase order for outsourcing supply?

There are no component parts related to the non-inventory purchase part on the PO Line when purchasing services for outside operations on a shop order. You are shipping a partially-completed manufactured part, and if there are any shop order components connected to the outside operation in the shop order (i.e., you provide these to the supplier to consume) these, along with the parent part, can appear on the Outside Operation Delivery Note. 

Components for Purchase Order Line pertains to outsourcing with an external supplier using the Customer Order flow, in which you are purchasing inventory part A from a supplier, and providing to the supplier (and possibly charging for) inventory parts B and C for the supplier to use in the manufacture of part A. In this case, you would use a buildable Product Structure of type ‘Purchase’ as mentioned by @Malsha Amarasinghe above.

Hi Malsha and Matt,

Thank you for the advice. I changed the part type to purchased and filled the purchased part structure and suppliers for purchase with the correct data. Now it is working properly

@matt.watters  good to know the addition information why the first set up did not work(part type manufactured)