English (Source)
Your Commander has already access to several towers. The first two are unique to your Commander and define their playstyle, many times being purely supportive. Build a few towers within range of the building, and make sure to build one which can actually attack.
Spanish Translation
Tu Comandante ya tiene acceso a varias torres. Las dos primeras son únicas de tu Comandante y definen su estilo de juego, muchas veces siendo puramente de apoyo. Construye algunas torres dentro del alcance del edificio y asegúrate de construir una que realmente pueda atacar.