Hoopa needs to be Unbound, and lvl 1 or 85 (For it to naturally learn it)
If Hoopa is lvl 100, you need a Heart Scale, then go to Fallarbor Town, then go inside the house in the top-left corner, and talk to the man. In exchange for a Heart Scale, he shall let Hoopa remember one of his moves, in this case, Hyperspace Fury. Note, that if Hoopa has never learned Hyperspace Fury, it will not work.
Hope I helped :D