I only have one disk?

I just bough a ps3 last week (im a pc gamer and would like to try console gaming). I bought this game and it only has one disk on it. Do i need to download the dlc? How Do i access it? What I have is the greatest hit Red dead redemption game of the year edition.

i have the 360 version and it came with 2 discs. one has the campaign and the other has multiplayer and undead nightmare.

I don't know if that is the same case with the PS3 version but I did not have to DL anything as it was on the second disc.

if you have the goty edition it all comes on one disk