You are about to play a 3D Tower defense game, you know what you have to do if you have played Tower Defense games, but I will talk about a few simple things you should do for those who do not.
Before the creatures arrive, you buy and add your defenses to the towers one by one with the money available at the beginning of the game, so the Creatures die for you and you can earn more money and add more defense to the tower. A99.io wish you have fun.