Minecraft wiki entry for Defeating_a_woodland_mansion, associated text: Use leads to move the iron golem around or lure a vindicator or an evoker into the iron golem's sight (make the vindicator or evoker follow you to the iron golem, evokers might be hard since they like to stand in the same place, best way is to stand at the edge of the evoker's line of sight and when it summons something it might move closer to you and follows you) and the iron golem will attack it, then you can lure more vindicators and evokers into the iron golem's range. Keep on repeating this process until you can't find any more illagers in the mansion. After that, you can loot the mansion, turn it into your base, or burn it down.