How and where to apply Resident permit?

hello all! I am Tunisian citizen and my son holding different passeport. I would like to come back to Tunisia and apply for him an RP (carte séjour/Resident permit) unfortunately couldnt find people to help me figure out how and where. thanks for your help :)

Anyone born to a Tunisian mother or father, is a Tunisian. Get a Tunisian passport for your son and enter Tunisia with him as a Tunisian citizen.