Should you want to change devices, please make sure you have saved your account, as is explained here. Saving your account is recommended to access it from a different device, but changing devices is rather easy and also possible by connecting your account with Facebook.

To access your account, first download the game from the app store to your new device. Once you open the app you will be presented with the main login screen below:

Then please use the "Login" option if you have saved your account and enter your username and password there or; use the option "Connect To Facebook" if you have previously linked your account with Facebook.