In order to move your city to another location in your present Kingdom, just select the desired tile and click it, then select the “Teleport” option:

Choose an item to use or purchase and then use:

You cannot teleport to the Kingdom’s Throne closer than five tiles. You cannot teleport your city to the territory of a clan which you are not a member of. Having teleported the city, you have to wait 20 minutes before you can do so again.