To redeem your earnings, go to My Account and then choose Redeem Earnings.
Your earnings are "pending" until 30 days after the order is placed. The 30-day window is in case a customer cancels or returns that order.
After 30 days, your earnings will move from the pending column to the redeemable column. You must have at least $30 in the redeemable column before you will be able to redeem said earnings.