Approve a purchase order and receive the goods — stock on hand increases automatically.
This is the step where a purchase order stops being a plan and starts being real inventory. Two things happen here, in order: approving the PO, then generating a purchase receipt from it — and only the second one actually moves stock.
Approval is a deliberate checkpoint before anything can be received — it exists so a draft order can be reviewed (right vendor, right quantities, right price) before it's allowed to affect real inventory. Once approved, the "Make" menu on the order offers a Purchase Receipt, prefilled with everything from the PO.
The receipt's quantity field defaults to the full ordered amount, but it's editable — this is exactly where you'd record a partial delivery if the vendor only shipped part of the order. Whatever quantity you confirm here is what lands in quantity on hand the moment you save.