Not sure how to cite a source? First, find out which style is required by your instructor (i.e. MLA, APA, or other) and then consult a guide for that style.
#Use of Sources: Citing
Citing sources is a way to identify and document the sources you used in your writing. Citing sources is a standard practice in scholarly and academic research. By citing sources, your readers can follow the trail you have provided and a way to verify the claims you make in your writing. Most importantly, you are acknowledging the works of others who came before you and their ideas you have used.
Citing a source used in a paper or other assignment is called a citation. The citation style or format is the way the set of details about the source is arranged.
The basic information about the source, like a book, will include the author's name, the title of the source (book or other material), place of publication, publisher, and date of publication.
If the source is an article within a journal or magazine, the details will also include the title of the article, title of the journal/magazine, volume and issue numbers, page numbers, and database if the article is from the Internet or from a library electronic source (i.e. database).
If the source of information comes from other types of material, other requirements of details about the source will be required.
--from libncsu
Watch this overview that explains why citing sources is important. (Skip any beginning ads/commercials.)