How do I access MGS 1 / 2 in MGS : Subsistence?

Recently, I went to buy Metal Gear Solid 3 : Snake Eater at my local Gamestop, but the clerk accidentally swapped the disc with MGS 3 : Subsistence. I read on www.Gamestop.com that you can play both MGS 1 / 2 on MGS 3 : Subsistence.. but I'm not sure how to access those. Do i have to beat the game first? I noticed in the main menu it says MGS 3 : Subsistence, Disk 1. Is it located on a second disk?