Place the chicken in your slow cooker and season it with salt and pepper.
Pour the salsa on top. Cover the slow cooker and cook on low for 6 to 8 hours, until the chicken easily shreds with a fork.
For the citrus salsa, combine everything together in a bowl and mix. Let it sit at room temperature for 15 minutes before serving.
To assemble the tacos, warm the tortillas (in the oven or microwave, whichever you prefer) and fill them with a few tablespoons of the chicken.
Top with the citrus salsa and queso fresco cheese. Serve immediately.