Maby its the wrong section but give then a proper answer if you know or not...
And there is only 1 way to do it, i would not recommend you that!
Plugin your PS3 HDD to your PC with a SATA cable.
Then Decrypt it, there are several tutorials on the forum.
Then Download DLC from a Illegal or Legal download. I Prefer Piratebay
Then use the pkg manager to extract all the contents of the pk3, there are also other ways but i dont know these at the moment...
Then install when not extracted or just simply play the game and look if it worked.
BUT AS I SAY:
I would NOT Recommend it!