This can be quite tricky first try.
Lord 1: They need lots of food (have lots Hunter's Huts or Hothouses with 1 or 2 Cookhouses. Soup (Law) can help a bit too.
Lord 2: They need to be healed. Don't build lots of Medical Posts or Infirmary till they arrived. I had a mission first go to build 4, but the other times just to heal a certain amount.
Lord 3: Resolve conflict. You need to stay in control for a Day which is easy. Hope above 50% and Discontent below 15%. I suggest you take the Faith Law path as there is lots of skills to lower Discontent. Either way, if you can reach the unlimited Hope Law, you only need to worry about Discontent.