How can I log in my account to another cellphone?

On your old device go to the Settings menu (three dots) and tap on 'Account' . Here you need to make sure you bind your game to an external account. If you have already bound the game then it will say 'Binding Successful' at the top.

Once it is bound. Start a new game on the new device. Once you are able to access the settings menu, go to the Account page again and select Switch account. You can then log in with the details of the external account that the game is bound to.

I would recommend not clearing the game from your old device until you have successfully logged in to it on the new device to make sure it works.