If you previously linked your progress to an account, you must open the game, log in to your previous Google Play/AppGallery/Game Center/Facebook account, and press the Connect button in the game's settings. The game will give you the option to load your last saved progress. Press OK and your progress will be restored.
If you did not previously link your progress, or this method of restoring your progress didn't work, then please fill out the tech support form and we will help you get your progress back.