How do you use more than 3 cannons?

[.:iLo:. Pois0n]

I'm playing solo and just unlocked 3 cannons but there doesn't seem to be any indication of what I need to do or unlock to get 3 cannons on my ship. What do i need to do?

[76561199209533650]

You can't have more than 2 equipped. The ones that you unlock can be swapped depending on which you prefer to use.