Rescue Ben King
Head to the Broken Shillelagh to start this quest. Once inside Ben King's simulation, walk forward until you spot some gang members. Take them out using hand-to-hand then kill the pistol-wielding thug to get that weapon. Continue to the church and take out more gangsters. When clear, head inside the church.
Exlore the church by following the markers. On your way to the third marker, you'll find King. Pick up the rifle on the table then help King fend off the attackers inside the church.
Exit to the graveyard and fend off more enemies. Kinzie will then advise you to check the shallow grave to get an RPG. Use this to take out multiple enemies at once. Keep killing them until you discover that King is bleeding out in the other side of the church. Rush over there and take out a few enemies along the way to clear your path. Revive King and clear off the remaining enemies.
Shortly after, Big Tony will appear riding a MG-mounted Humvee. Kill him then proceed to the next marker. You'll find Tanya and some of her gangsters there. Take them all out to complete the quest.
Completing this quest will add Ben King to your crewmates and as a homie. Several side quests given by him will become available as well.