The "Change Device" link that lets you transfer data to another device only appears if the new device has no pre-existing game data. If the link doesn't appear and you need to transfer your saved game data to a new device, follow these simple steps:
For Android users:
1. Go to Settings > Application > Application Manager > All > Dragon Project and Select "Clear Data".
2. Launch the game. You should see the "Change Device" link now.
For iOS users:
1. Tap and hold the Dragon Project app icon until it starts to jiggle.
2. Tap "X" and then agree to delete the app.
3. Visit the App Store to download Dragon Project again.
4. Launch the game. You should see the "Change Device" link now.
Note that once you transfer the game data to a new device, all pre-existing game data on that device will be overwritten.