In Arkansas, until you're 18, you're still considered a minor and you have to live with the parent who has custody. If your mother wants custody (and you want to live with her), she will need to file a motion to modify custody, OR your mother and your father will need to both sign an Agreed Order changing custody from him to her, and the judge would probably sign that order. These are things that need to be handled by a lawyer. If your father and mother are both in agreement, it should be very simple to do, unless there is some huge reason why a judge would think you are not safe with your mom (if she's an alcoholic with a string of DWIs or if she's an illegal drug user, etc.). But barring that, at your age, a judge will really listen to you and why you want to live with your mother and there is a good chance your father would agree rather than go to the expense and trouble of a court battle that there's a good chance he would lose.
The best choice is ALWAYS to do it with agreement of the parties. Court battles are no fun for anybody, least of all you. If this is really what you want, and if your mom wants you to live with her, try to talk to your dad and explain that you miss your mom and need her and you want to live with her. As long as he knows you'll be all right and be safe, maybe he'll agree to it without the need for a big fight.
But unless the court signs an order transferring custody from dad to mom, custody remains with your dad and you could definitely have legal issues if you try to just up and move in with her.
No attorney-client relationship is established with this answer. It is not to be considered legal advice, but is merely given to point you in the right direction and give you a general answer as to the law regarding the question you have asked.