First, in an essay, you'll need to introduce the quotation by indicating both who said it and when. Then, you will need to transcribe it word for word, including all the punctuation, placing the entire quotation in double quotation marks. Then, after the quotation, you would place the author's last name and page number where you find the quotation in parentheses, followed by a period. Finally, you should then spend a few sentences explaining what the quotation means and analyzing it in order to show how it helps to support whatever claim you are making in your essay.
It might look something like this:
Mrs. Putnam, growing more and more frustrated and desperate in her search to find a reason for the deaths of her seven children, confronts Rebecca Nurse with some suspicion because of Rebecca's incredible luck in childbearing. Mrs. Putnam says, "You think it God’s work you should never lose a child, nor a grandchild either, and I bury all but one? There are wheels within wheels in this village, and fires within fires!" (Miller 28). It doesn't make sense to her that she should lose so many children and someone else should be lucky enough to lose none. Why would God seek to punish her in this way? She believes that He would not because such a punishment would be unjustified. Therefore, she comes to the conclusion that it must be the Devil's fault -- his and anyone who works for him -- that she has lost so many babies. She believes that there must be those who work for the Devil, i.e. witches, living in Salem, and she faults them for her terrible misfortune.