1. Start the game by clicking on the "Play" button.

2. The game starts with your character standing on a street, and your goal is to defend against the incoming waves of zombies.

3. Use the button to aim and click to shoot the zombies.

4. As you progress through the game, you'll earn money that can be used to purchase upgrades for your weapons, barricades, and other defenses.

5. You can also purchase new weapons and ammunition to help you defend against the increasing numbers and strength of the zombies.

6. Be careful not to let too many zombies get past your defenses, as this will eventually lead to your defeat.

7. Use your earned money wisely to improve your chances of surviving each wave.

8. Keep playing to improve your skills and beat your high score!