If you don't remember how to get to the Iifa Tree, return to the Conde Petie Mountain Path and take the one path to the north of where one of the stones was on your first visit. From there, it's a hop, skip and a jump away from the Iifa Tree. Upon entering, there will be a short scene, then you will have the option to change up your party members and change their equipments. For now, this walkthrough will use the party outlined at the end of the previous page, which will be Zidane, Amarant, Vivi and Eiko. You can still exit the Iifa Tree at this point, but you can't change your party members around (like substituting Dagger back in), although re-entering will give you the prompt again.
Travel along the path before you and after some screens, the game will automatically take over for you. Once the scene is over, you will have another opportunity to change around your party members. Watch the scene that follows, then you'll be thrown into a battle with two Mistodons. These undead creatures are nothing more than a normal monster, so you won't really have to worry about anything. If you wish to get rid of them quickly, then you can simply have Eiko or Dagger cast Life on them, but their HP pools are pretty low, so there isn't really any point in doing so.
More scenes follow this battle and when you can move, look behind the tree nearby to find Mocchi, a moogle. You can save your game here, although it's not really needed, plus you can read a letter from Stiltzkin if you select Mognet. There's only one way to go here, so follow the path before you, knowing you'll have to fight a few more Mistodons. Once you reach the end and meet back up with Dagger, you'll receive an Aquamarine and there will be more scenes occurring here, bringing an end to Disc 2 and taking you straight to Disc 3.