click play and select the dificulty (easy, normal, hard). click on the item you want and place it where the info tells you to place it. most items automaticly fight for you, but you can buy a turret and manually control it (to control it, hold the mouse down on the turret and aim, then let go of the mouse). click the green triangle at the bottom to start the next wave if there isn't a wave in progress. click the green triangle with 2 lines to listen to different music (yes, if you keep clicking it you'll soon have the same music again, so don't worry). You can also press space to attack bosses.
