To create an account, you must have a Gmail (Android) or Game Center (Apple) or Facebook (Android / Apple) account.
To change the account, go to the settings, and to account:

You click on Connected:

You have the choice between Google Play (Android) / Game Center (Apple) or Facebook (Android / Apple) or MyGames (Android / Computer / Apple) :

Subsequently, the game will ask you if you want to change accounts or not:

For any action, to delete his account or to unlink his account, it is sufficient to send identity files to the support (Assistance) in order to prove that it is not another person.
When you delete your account, only your information will be deleted, the account will still belong to the MyGames company.

To create another account, just create another Gmail or Game Center or Facebook that is not linked . When players tell you if you are a reroll, it is simply that you have another account.