1. Click on Moonfeather/heart (i forgot her name lol) and listen to her story when you are a warrior.
2. Get the moss-ball from the warriors den and place it on the red X on the shore.
3. Wait a day
4. Click on Mosskit/Moss-shadow and bring them to Bramblestar.
5. Afterwards you need 60+ reputation and Bramblestar will make you leader.