Once you have downloaded the game onto your device and have opened it please go through the tutorial. You can tap through each step quickly. At this time you will be signed on to a guest account.
From there simply scroll the Menu bar at the bottom of the screen all the way to the right > tap ‘Settings’ > tap ‘DECA Account’ > then enter your login credentials.
At this point, if you still see a new city, you’ve been put into a new realm and need to log into the previous realm where your city was located. To do this tap on your current Level in the upper left hand corner > tap the Realm tab > then locate your previous realm and tap Return.