Knights & Merchants
Open the inventory window by clicking on a Storage House and click once on the following items.
A red triangle will appear in the item's square as each is selected.

Row 1, item 3 (Wooden Boards)
Row 2, item 2 (Iron Bars)
Row 2, item 4 (Wine Casks)
Row 3, item 1 (Bread)
Row 3, item 5 (Cooked Meat)
Row 4, item 1 (Animal Hide)
Row 4, item 5 (Plate Mail)
Row 5, item 1 (Hand Axes)
Row 5, item 2 (Swords)
Row 5, item 3 (Lances)
Row 5, item 4 (Pikes)
Row 5, item 5 (Long Bows)

Then, click on Row 6, item 1 (Crossbows) to add 10 of each item to your Storage House or on Row 6, item 2 (Horses) to complete the current mission.