To add stock, you can click on the ellipsis [...] in the Stock Code field, or enter the stock code which will bring up the Stock Select grid displaying any purchase orders for this stock which have a balance remaining. Otherwise, you can select the ellipsis [...] within the Stock Code field to display the Stock Select grid and use the Filters and Apply to locate the stock.
Once you have located the stock code and the purchase order, you need to reduce click OK.
Further information: