When entering the application for the first time, you will need to register with a Facebook account or an email address to start playing.
In case of using an iOS device, you will also have the possibility to register in the game through your Apple ID. If you select that option, the game will create an account with your Apple ID information.
Keep in mind that game information, such as statistics and purchases made, is associated with the account. This is why it is not possible to change the email address, as all the player's achievements would be lost.
On the other hand, if you have created your account with an email address, you can still link it later to a Facebook profile.
We recommend you visit the articles: "Can I modify my email address associated with the game?" and "How can I link/unlink my account to my Facebook profile?" so you can get more information.