cheating-is-good

Well, the Black Star Dragonballs are the one from the GT saga if I remember correctly. When I obtained all Seven, it brought forth the Red dragon, Shenron. Anyway, in order to obtain all Seven of the BlackStar Dragonballs, I suggest that you go into Dragon History, and play the GT storyline Saga. While playing it, search for the Dragonballs in each stage. You should find one in every stage. Eventually, you will have all Seven. Once you find them, you will have to head to the main menu, and select the call Shenron option. Then, you will be granted a wish.

Hope this helps.