Your user ID is unique to your game and helps us locate your data. It can be found in the settings area (by tapping the cog wheel icon). We recommend having your user ID written down somewhere safe (preferably not on your device) so that if you ever get separated from your game, the support team can find it again and get you reunited!
You can not login using the user ID so if you ever need to change device we will need this to help you too.