Armaments include weapons, shields, and armor that can be added to your inventory. In the Gear section, you can add an armament to your inventory by selecting an armament class (Weapons, Armor, or Shields) and clicking Add to Inventory. This will prompt the Selections Sidebar to provide you with a dropdown to choose which armament from the class you'd like to add to your inventory. Click Buy if you want the item's gp cost to deduct from your total gold; click Add if you want the item to be added to your inventory for free.
Selecting Armaments in an Class
When you select a specific armament in a class, this is a purely aesthetic choice you're making. All weapons in the Blunt class (Spike Hammer, Spiked Club, Spiked Mace, etc) have the same mechanical attributes. The same is true of specific armors or shields in their armament classes.