Some people take their sail to a sail maker to have the slugs put on ($70-100) and some people do it themselves. A sail maker will usually install grommets in the sail and fasten the slugs to them with shackles.
It is not a hard job to add the slugs to the sail at home using slugs and plastic shackles. In this case there are no grommets used and the shackles are held in place by a screw through the sail. This sounds crude but the shackle pinches on the rope and the screw just holds it there. The slugs and shackles can be purchased from marine catalogs or sailrite. Most people put on 10 to 14 slugs. The top one should be as close to the top of the sail as possible. The others should be equally spaced along the luff. Do not place any near the reef point.
If ordering from Sailrite the recommended slug no is 23308 and the shackle no is 24105.