-Click on one of the seeds on either side of the screen to select it.
-Click on the lawn to place whatever you have selected.
-Click the plants and zombies to delete them.
-Click the pause button to pause the plants and zombies (you can still place while paused)
-Click "clear" to delete everything on the lawn.
-Right now, only day plants and zombies are present.
-You can just play around with the plants and zombies.
-You can also set up some plants and then try to penetrate the defense by placing zombies. That's fun (: