In Castle Siege, the first thing you must do is claim land. The best land to claim is near trees and water. You must cut down the trees, while avoiding the falling timber.
You must use this wood to build walls around your property, otherwise you will get sacked and looted by enemies (mainly goblins. I’m obsessed with goblins).
In your claimed land, you can build mine shafts, wells, barracks, stables, farms, guard towers, training camps, a castle, and other things.