The story is told in third person limited, from Will's point of view.

You can tell a story’s point of view first by looking at the pronouns for the narration.  If you see the pronouns “I” and “my” a lot, then you know you have a first person narrator, for example.  It’s a safe bet!  A first person narrator tells the story as if the character is speaking directly to you.  If you see a lot of “he said,” or a character’s name, such as “Bob said,” then you know you probably have a third person narrator. 

With a third person narrator the author does not directly seem to be telling the story, and there seems to be an intermediary.  It is a bit more distant.  There can be some “they” and “them” and other third person pronoun use instead of the first person pronoun use.  It is less personal.

From there, it gets a little more complicated to determine if the story is in third person limited or third person omniscient.  An omniscient narrator uses every character’s point of view.  It is godlike.  A third person limited narrator follows one character.  It is limited, like first person narration.

Now that I have given you some background, it is simply a matter of looking at some textual evidence.  Do not look at dialogue to determine point of view.  You can look at dialogue tags, where it says who is speaking, but not the dialogue itself.  Look in the narration itself too, to determine if you see “I” and “we” or “he” and “Will” when the main character is thinking.

They walked along without speaking for a few minutes. Will deliberately set a fast pace, but Meg seemed to have no difficulty keeping up. Finally she broke the awkward silence. (Ch. 3)

In this paragraph, we are told what Will was thinking.  He intentionally walked quickly.  He feels that Meg has no trouble keeping up with him.  We also know at the end of the paragraph that he felt that the silence was awkward.  These are all Will’s thoughts and perceptions, not Meg’s.

Here is another example where we can clearly tell that the only perspective being told in the story is Will’s.

Will just stared at him. Who else would he be hollering for in the middle of the woods? And then he understood. His uncle wanted to be called by name. Well, he wouldn’t do it, and he hoped the man knew why he wouldn’t! (Ch. 4)

In this paragraph, we can again see the use of Will’s name in the narration, and also the third person pronoun “he.”  You can also tell how the paragraph is slanted to Will’s point of view, and does not include his uncle’s.

Third person limited allows the author to closely follow a character, but have some distance too.  In this case, there is some room for bias.  Will is definitely a biased character.  He feels hurt and angry because he was orphaned in the Civil War.  He is going through some things.  The more personal narration allows the author to follow Will alone, where an omniscient narrator would not be able to.  However, the third person allows us to be a tad more objective than first person might.