How do you equip different turrets? Plz help – Block Fortress: War Review

I have been playing this game for a while now, and it is a great game! But I’ve run into a problem I can’t solve. I just bought the 50 cal turret, and I have no clue how to be able to equip it so I can use it. I have been searching all over YouTube, and I have even watching gameplay videos to see if they ever equip a turret. But I never found an answer. So can someone please tell me how:)
Review by BernieGiam on Block Fortress: War.