they are automatic, and i believe they got released the sunday before the event.
The 3 point contest, is decided by a formula, i am not so sure about it but it considers the amount of taken 3 pointers and to a certain degree there percentage. If i had to answer i would say, that every 5 made 3 pointers a new player group is created which is ordered by shooting percentage. the 6 best shooters are taken for the contest.(the made 3 pointers are also the tiebreaker in case of a tie)