Resources
Before beginning to consider founding a new city, a player must accumulate 10,000 of each type of available resource. The various resources must include food, wood, stone, iron and gold. The balance is deducted from your capitol city's coffers, so your resources must be stored there. Resources accumulate over time from the rural fields surrounding a city.
Waging Warfare
Any new plot of land a city can occupy is defended already by some type of enemy. This foe must be dispatched before claiming the land. Build a barracks in one of your cities and train various types of soldiers within it. By upgrading the barracks and researching technologies, you can develop stronger and more versatile armies.
Founding Cities
To found a city from scratch, simply send your soldiers to attack a plot of land and defeat all enemies occupying it. When the battle is complete, if your character has enough "nobility points," you can click the "Enter" option to begin founding the city. Nobility points are acquired by upgrading your government rating while filling your coffers with increasing amounts of resources. Of the 10,000 of each resource sent to a founded city, 5,000 will remain to develop its defenses and infrastructure.
Conquering a City
Two primary differences exist between conquering an empty piece of land and conquering a city. Chiefly, city walls have fortifications with the ability to do damage, so your troops must be directed carefully to keep them out of harm's way. Destroying a wall is one condition that must be met to conquer the city. The second difference is the allegiance civilians feel toward their lord must drop to a rating of zero. This happens over time, following repeated attacks. It can be useful to send "scouting units" to examine a city before attacking so you know what waits for you.