Place the chicken and enchilada sauce in the instant pot and cook on high pressure for 15 minutes. Let sit for 5 minutes, then manually release the pressure. Shred with two forks.
To cook slow:
Spray a slow cooker insert with cooking spray.
Place the chicken and enchilada sauce in the slow cooker and cook on low for 8-10 hours, or on high for 6 hours. Shred with two forks.