Players with an existing Animal Jam Classic account can use their logins to access the Animal Jam app.
Keep in mind that Animal Jam Classic and Animal Jam are two separate games so nothing on the account is shared between the games such as animals, items, pets, and currency. There currently is no way to transfer in-game items and such between the games.
Parents can manage both of their children's Animal Jam Classic and Animal Jam accounts from their Parent Account. To access this, log in at the parent section of the Animal Jam Classic website.