Product recipes must be defined in Products application in order for you to use them with manufacturing orders.
When creating a new manufacturing order for a certain product, after you select the product and click on the [CREATE] button, product recipe items are automatically added to the manufacturing order if there is a defined product recipe for the selected product.
The quantities for the items are automatically calculated based on the Quantity (number or products that will be produced with this manufacturing order) and Quantity per unit (defined in product recipe).