Revan,
Happy New Year. I will give a brief overview and then use the attachment for additional help (its manual on Subcontracting process).
Subcontracting:
In Manufacturing you can define a Routing Line to point to a Work Center that is defined as a Vendor (Subcontractor). When an Item, who uses the Routing, is in demand, you will utilize the Subcontracting Worksheet to generate Purchase Orders. When you post a Subcontracting PO, BC will automatically posts the necessary information to the Production Order.
The above is a high-level overview but use the attached to walk through the process. It is very simple. If you have more questions, feel free to write back.
Thanks,
Steve
80550_5F00_ENUS_5F00_MANI_5F00_SubContracting.pdf