Please note all account progress on the first (original) device will be Gone when the transfer is finished.
In the main screen, tap the Settings button in the top right corner - it looks like a gear.
In the Settings menu, tap the button "Link Accounts":
In the next screen, tap the button on the left "Generate Code" to get a unique code.
On your second device, navigate to the Link Accounts screen within the Settings and then tap on the "Enter Code" button.
There, enter the unique code you received on the first device and confirm.
Please note all account progress on the first (original) device will be Gone when the transfer is finished.
If you are still having issue transfering account, please send a ticket to Customer Care for assistant.