In particular, you should take great care to avoid plagiarism, which is copying something written by somebody else without giving appropriate acknowledgement. It is plagiarism to copy another student's essay. Should completely or partially identical essays be submitted, neither will receive any marks. Copying published material is plagiarism too if the sources is not appropriately acknowledged. Essays containing unacknowledged copied material will be return with no marks.
Documentation involves citations and references.
Different academic disciplines have different conventions about these. You are asked to follow those current in Anthropology. The proper formats for citations and references are illustrated below. You should follow them exactly, paying particular attention to the punctuation. What is reproduced is exactly what Firth wrote, so it is within quotation marks and attributed to a particular page in a particular book by Firth.