What do you need?
1.Some Bandit Leaders as prisoners
2.Some prisoners
3.When you speak with him,tell him to hunt sb down
4.He will take all your prisoners with him to do your quest, follow & tell them to join you
4.5(consider having enough pennigans with you,or you probably will have to fight them again)
4.75 If they dont want to join,click down "leave" & repeat it a few times until they do
5.Voila,you now have your old enemies as allies^^

Btw:if you have problems getting bandit leaders alive; use that guide from myself to fix it. https://steamproxy-script.pipiskins.com/sharedfiles/filedetails/?id=1437703857