How to upgrade my APC?

Each APC is provided by a barracks building in your city. Barracks 1, 2 and 3 and the Class Barracks. Upgrade the barracks buildings to increase the amount of troops you can add.

Each APC also have its own research tree in the Institute. Compete the research items to improve its performance, and let you add heroes to the Formations.

Add the heroes, then unlock and upgrade the heroes skills to let you add more troops and have better attacks and defense.