after your a warrior talk to milkwillow, shell ask if you can find her a good den (make sure you have 160+ health) go to the hunting grounds and go to the right cave there should be a badger there, fight the badger and talk to milkywillow again so she could get her new den, then, talk to moonheart, shell ask you if you want to hear about mosskit,after she tells you go into to warriors den and pick up the moss ball, then go to the shore and place it on the X wait until night and mosskit should appear, go to the highrock where bramblestar is, if you have 80+ reputation then he'll make you leader, if you don't then once you have 80+ then he'll make you leader then :D
I made some art lol