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.

Thanks to Revolution readers Johan Johanson, Tazman, Liam v. Veen, Kougen, and Gary!