How do you equip an Aquila with ultra guns in Steel Sentinels

To equip one ultra gun to your aquila, you can either put an ordnance mounting on the shoulder slot and then select the ultra, or put an Orion arm on the arm slot and then select the ultra gun. The aquila can equip up to 2 ultra guns max (just simply put ordnance mounting and an Orion arm on your aquila and choose 2 ultra guns).