Set a sauté pan or a large skillet over medium heat. Place the chicken breasts in the skillet and pour in the salsa, water, ancho chili powder, cumin, salt, and pepper. Stir everything to coat the chicken well.
Cover the pan and let it simmer for five minutes. Flip the chicken and stir the sauce. Cover again and simmer for an additional five to six minutes, until cooked through.
Remove the chicken and shred it using two forks. Return the shredded chicken to the pan, stirring it into the sauce. Reheat if necessary.
Assemble your tacos by filling tortillas with the chicken mixture and topping with your favorite toppings.