This Chapter is a very important one for a number of reasons. Huck Finn is going to the Phelps's house because he knows that this is where Jim is because the Duke and the King sold him to Mr. Phelps. He has no plan on what he is going to do or say, but he just trusts in Providence or fate to help him out. Note what he says:
I went right along, not fixing up any particular plan, but just trusting to Providence to put the right words in my mouth when the time come; for I'd noticed that Providence always did put the right words in my mouth if I left it alone.
As he goes in then, he realises that The Phelps's are actually the Aunt and Uncle of Tom Sawyer, and what is more, that they have mistaken Huck for Tom Sawyer himself! This enables him to be welcomed in to the family and to find out where Jim is being held and to plan his escape. This is how trusting in "Providence" actually helps Huck in this Chapter.