To build a new city, you need 100 relics.
Assuming that you already have gathered 100 relics, go to your Sage’s Tower (from your first city), click on “Relics”, “second city” or “third city” > “claim”.
Now you need to conquer a plain. Go for a plain that is located near your main city. A trick: get a plain a bit to the right from your main city. Attackers are usually scrolling left and down because is more comfortable to scroll that way.
Anyway, conquer a plain, recall your troops.
Now, from your main city, from the top, click on your city’s name, you should see a green icon for your second / third city, depending what city you have to build.
Click on the icon > click on your plain > name your new city > create. Restart the game.
Send some resources to your new city and start building. First thing to build? A vault so you can protect your resources.
If you have any tips, please share them in the comments.