1Cut avocado in half; remove pit and avocado peel. Cut halves into slices. Sprinkle with lemon juice to keep avocado from turning brown.
2Heat oil in 10-inch skillet over medium heat. Cook chicken, chiles and onion in oil, stirring occasionally, until chicken is hot. Heat taco shells as directed on package.
3Spoon about 1/4 cup chicken mixture into each shell. Top with cheese, olives, lettuce and avocado. Serve with taco sauce and sour cream.