Adding any chlorine is done on a need be basic. If it is just the two of you, it might be never. If you have a party and the hot tub gets heavy use, then it is a good idea to add some afterward. If you use bleach, probably 2-3 ounces is sufficient unless the water is in bad condition, then 6-8 ounces may be necessary. If you use liquid pool shock, it is twice as strong so cut your dosage in half. Also, have your dealer test for phosphates. High phosphates can prevent salt systems from producing chlorine, or at least reduce how efficiently they do so.