Just place towers and watch them kill zombies. Make sure your base doesn't die from the zombie though. -- NOTE -- THE GAME IS STILL IN WORK IN PROGRESS, STAY TUNED! Also, if zombies no longer spawn then it means that the waves are still in progress. P.S. All the towers that aren't modified and replaced yet are nerfed lol.
--IMPORTANT-- Most if not all towers and enemies are based off the towers and enemies from the Roblox games, Tower Battles, and Tower Defense Simulator.