Where is the option to install the disc 2?.. I just get the option to play it.
You do not need to (and probably shouldn't) install disc 2. Disc 1 needs to be installed, disc 2 should be in the drive when you play. Installing disc 2 is possible but, from what I've heard, has little to no noticeable improvement, still requires you to use the disc (to stop you installing it then selling/returning/lending it) and can even make things worse.
If you still insist on installing disc 2 for some reason, you can install it in the same way that you would install any other game.
Disc 2 is the disc that you play the game on, disc 1, which is the one with the bikini selfie, is the install disc. It will not let you play the game, however, if you either A.) Have not installed disc 1 on to that specific console, or B.) It has already been installed onto another console. But again, remember that disc 2 is the play disc and disc 1 is the download disc.