You will be contacted by an attorney from the Defense Appellate Division for your service. If you are in confinement, the counselors can advise you as to how to contact that attorney.
You should consider whether you want to retain a civilian attorney to represent you. Every case is different, and some lawyers are more experienced at certain types of cases than others. Military defense counsels tend to carry heavier case loads than civilians, and it may be in your best interest to consult with civilian defense counsel. In addition, military defense counsel tend to leave their assignment before an appeal is completed, and you may find yourself with several different attorneys for your court-martial appeal.