It depends. If the title screen is the one with the expansion symbol on it, then you should be able to go right into the expansion by reloading your save file (some cutscenes will play out and you'll get teleported to where the entrance to the World of Dreams is), if it's the non-expansion title screen (which has all your regular party members on it and not just Saya, Yukari, and Nightmare Yukari), then there's a code that should have come with the game that you need to enter in the launcher.