Be sure to know if your professor has requested you use a specific style for citing, otherwise, choose one style to follow, and remain consistent throughout your work.
The most common citation styles used in Economics are APA and MLA.
Citing Sources (includes information specific to APA, MLA, and others).
Zotero is a free app (desktop+online) for organizing your citations/references and inserting them into your Word, Google Doc, or LibreOffice text.