There are a few ways to go about this
Build a new city on an empty spot on the map. You can build a new city at lvl 4 and every 3 lvls after. Simply go to the map, find an empty soot and select it, hit enter, and create city. This costs 2,000 of each resource, so be sure you're well prepared
You can also steal a city at lvl 4 and every 3 days after.
Stealing a city takes 10 total attacks on a branch city. You can't steal a main city. However, there is a 5 attack limit per player per day. So you'll want to get a friend to help you out. The first attack should be strong enough to clear the defences of the city, and as long as the city owner does not fight back, all you need is one cav after that.
Good luck and haypi hunting
