Every time you use a primary or secondary source, you must give credit to the work of the author. If you do not follow this guideline, you are plagiarizing, which is considered an offence in the academic world. All information that is directly quoted or paraphrased (in your own words) must be cited.
There are several styles of citation:
MLA
APA - mostly used by courses in senior grades and post-secondary courses
Chicago
Harvard
In APA documentation style, you acknowledge your sources by indicating brief parenthetical (in-text) citations in the text of your report with brackets. They must match the secondary sources listed in your References page.