Players with existing Animal Jam account can use their logins to access Play Wild.
Keep in mind that Animal Jam and Play Wild 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 their children's Animal Jam and Play Wild! accounts from their Parent Account. To access this, log in at the parent section of the Animal Jam website.