You can cook raw chicken in the slow cooker and the slow cooker will fully cook the chicken along with the other foods within 8 to 10 hours.
The slow cooker will cook the chicken meat and make it soft and the chicken will usually fall off the bone easily as well.
Or you can brown the chicken some before putting the chicken into the slow cooker if you prefer to do so.
I sometimes will brown chicken before cooking it in the slow cooker if I want browned chicken which gives it a good flavor.
Other times I would just put the raw chicken once thawed out directly into the slow cooker and allow it to cook the chicken to where it's soft.
If you put frozen chicken into the slow cooker it will cook but will take longer to cook.