A citation is required if you paraphrase (use someone else's ideas in your own words), summarise (use a brief account of someone else's ideas), quote (use someone else's exact words) or copy (use someone else's figures, tables or structure). Insert a note reference number at the end of the relevant sentence:
...emotional involvement with which she recalls and recounts the events of her youth.1
The superscript number should follow any punctuation. Notes should be numbered in sequence throughout the assignment.
Give the full details of your source in the footnote the first time you refer to it. This enables the reader to check a quotation or the evidence on which an argument is based. Later references to the same source should be given in an abbreviated format.