For all the people who are wondering How to "Unlock" their ps3 DLC's and stuff; follow Every thing that Glaciusx25 shared; except for the Last part: "After this quit BF4, go to games and apps from the dashboard and then manually install each expansion. After this start BF4 and you can play on the new expansions as a premium player." This step is unnecassary, as some confusing.
Instead, for the Last Step, and IF you actually said "Yes" to transfer your ps3 account info over to your new ps4 -if not, you're Toast!- the just go to the Game WITHOUT "Starting" It; and look for "Related Items." It is in here that you will find ALL of the DLC's... Or, you can look to the Right, where it says: "Review All". All of the BF4 DLC Add Ons will be in there as well. The one's that you had previously on the 3 will say "Free." Just DL them and shag your tail in there so I can keel you! ;-)
Welcome to the Battlefield Maggots... muaahahahahah