This is a message that Harper Lee repeats throughout the book. Atticus always tells his children to put themselves in someone else's shoes before you pass judgement on them. The quote you gave above is when Scout has problems communicating with Miss Caroline, her teacher. Atticus is telling Scout not to judge Miss Caroline too harshly because she wasn't from Maycomb and didn't know its history or the history of its inhabitants.
When Jem speaks harshly of Mr. Cunningham's behavior during the mob scene at the jail, Atticus tells him,
"That proves something---that a gang of wild animals can be stopped, simply because they're still human.....you children last night made Walter Cunninham stand in my shoes for a minute. That was enough." (pg 157)
When Bob Ewell spits in Atticus's face, Atticus tells the Jem,
"Jem, see if you can stand in Bob Ewell's shoes a minute. I destroyed his last shred of credibility at that trial, if he had any to begin with. The man had to have some kind of comeback, his kind always does." (pg 218)
Atticus is trying to instill in his children an understanding of people . He wants them to make good decisions and not judge people harshly. If you can put yourself in another person's situation, then you will make wiser decisions.