As you progress through the story in State of Decay 2, you'll eventually finish up the Friendly Neighbor mission, which will allow you to unlock a Leader that will help you on your way to making your community a large enough one to keep the town safe from the plague.
While changing your Leader does impact what quests you will have (and what Legacies you earn after completing the game - more on that below) as well as give you some extra facility options, it doesn't really change much in terms of gameplay.
Nevertheless, what kind of leader you want should be thought about for at least a few moments, as the facilities that they have and the legacies they will grant you will appeal to different kinds of players. So with that, let's get on to how to change your leader.
If you've just finished the Friendly Neighbor mission and have yet to choose a leader, then you will have the easiest time with this. Simply have your character gain enough standing in the community to become a Hero (by doing missions and killing zombies), and then highlight the character in the Community tab of the menu. The game should tell you what button to press on the bottom of the screen for the leader, so press that, and then you'll be good to go!
It should also tell you what kind of leader you might have if you make that character your leader. You should know what kind of leader you want beforehand, as the legacies will change depending on your leader as well as the facility upgrades they offer.
If you already have a leader, then the only way to change the leader is to have them die or be exiled. Get all items off of them, go into a group of zombies, and let them kill the leader and you should be able to repeat the above for a new character.Legacies are bonuses that are obtained after completing the game with a specific kind of Leader. Each one has a different bonus, and there are some that will appeal to other players more than another. This is why it is important why you choose a leader after you decide on what you want out of your bonus. When you start your next community, you get the option of choosing up to 3 legacies that you've unlocked prior, so it might be in your best interest to pick a specific Leader so that for your next community, you get the best bonuses to make the missions that much easier. Receive a giant pile of guns, ammo, and grenades when you settle your first home.Receive a pile of high-quality loot from old friends once a day.Receive a visit from a friendly trader (and 4000 influence) after you settle your first base.Base-wide power and water with no fuel cost or threat.