Both of the previous answers are correct, in fact, if you ALREADY had premium activated, your prize was just added to the expiration date of your premium as
@Clarky said.
On the other hand if you did not have premium activated, it got added to your account but it requires a synchronization to happen so you get the perks of being premium. That can be achieved by talking to the NPC at City Hall or reconnecting as
@IZ_ said.