There are different styles of citation, American Psychological Association (APA) is recommended for social science. If you are not assigned a style for your assignment, it does not matter what you use as long as you are consistent and use the same style through out. You will use in-line citations and a reference list at the end of your work.
Zotero is free open access citation management tool that you can download and use as a web browser widget. Learn more on the Columbia University Libraries Reference & Citation Management webpage.
All knowledge is built from previous knowledge. As you research, you create your own ideas based off of what you have read or watched. When you put your ideas on paper, you must distinguish between the building block ideas borrowed from other people by citing the sources that inspired your line of inquiry. Readers should be able to find each source you have mentioned through your accurate citations.