You need 10,000 food, 10,000 lumber, 10,000 stone, 10,000 iron, and 10,000 gold. In addition, you need to own at least one flat and have 250 workers available.In order to build the X amount of cities, these are the Titles you need:
1st City - Civilian 2nd City - Knight 3rd City - Baronett 4th City - Baron 5th City - Viscount 6th City - Earl 7th City - Marquis 8th City - Duke 9th City - Furstin 10th City - Prinzessin
Please keep in mind that you will need the required Rank, medals, and gold to advance through the Titles.
To actually build your city, you need to click on the flat that you want to build your city at, and click “Build City”. You want the allotted time, and then BAM! - you have your next city!