1) Pick a task, which Amazon calls a HIT. "For example a HIT might ask: "Is there a pizza parlour in this photograph?" Typically these tasks are extraordinarily difficult for computers, but simple for humans to answer."
2) Find Waldo.
3) Profit! "The money you earn is deposited into your Amazon.com account, where you can turn it into cash at any time by transferring it to your personal checking account."