As you gain more men, renown and power in Mount and Blade 2: Bannerlord, you'll eventually want to secure a settlement as your own. Regardless if you choose the direct or indirect method, you'll have to put in some work.
Here's everything you need to know about how to get a settlement for yourself in Mount and Blade 2: Bannerlord.
Mount and Blade 2: Bannerlord How to Get A Settlement
The direct method of getting a settlement in Mount & Blade II: Bannerlord involves, as you can probably tell, using brute force to siege it and defeat its defenders. In order to do so, you'll first need to be at war with another faction.
Getting someone to hate you enough is terribly simple, though. Just raid one of their villages which, aside from pissing off the owner, also yields loot for your army.
Once you've done that, you're free to select a castle or town to siege. Early on, you'll want to target castles as even with smaller defending armies capturing one does require quite a bit of effort.
You'll need a sizeable army of your own as you'll likely have to deal with both its defenders and additional troops the owner might send your way.
Siege weapons can also make your life easier, destroying fortifications. How quickly that happens is determined by your character's Engineering skill.
Once you've dispatched the outside troops, if any show up, lead the assault in the inner garrison. You'll have to fight your way through them, victory transferring the castle's ownership over to you. You also take control of any villages under the castle or town's control.
The indirect method of getting a settlement in Mount & Blade II: Bannerlord involves being someone's vassal. If your liege isn't a complete idiot, they'll eventually conquer towns or castles and, if you're pulling your weight, you'll receive some of them as your own.
Simply getting a settlement, however, is just the first step as you'll then have to worry about keeping its people fed, protecting it against sieges and assigning someone to lead it.