Secondary sources are scholars who write articles or books or lectures. Those scholars are qualified to write by education and further study that has made them expert in some field of research on primary sources of a certain type. Secondary sources analyze and interpret primary source information, seeking to explain how and why it exists as it does, where it came from or where it is going, what it means, how we know the answers to those questions, etc. Secondary sources are the means by which scholars communicate with each other over distance and time, and the paper you are producing is an example of just such a secondary source for others working on the primary source information of the same type as that which you have. For that reason, you can use good secondary sources in your discipline as models for how to write your own papers, following their documentation styles, applying their theories of evidence and analysis, using their terms of art, and trying to imitate their strategies for generating insights, which you can begin to infer from their writing.
In the two-item Works Cited section below, which is the primary source and which is the secondary source?
Bawcutt, P. “The Mystery of The spyte of Spaine (Heirs of Andro Hart, 1628).” The Bibliotheck: A Scottish Journal of Bibliography and Allied Topics 19 (1994) 5-22.
The Spyte of Spaine, or, a thankfull remembrance of Gods mercie in Britanes dileuerie from the Spanish Armado. 1588. Edinburgh: Heirs of Andro Hart, 1628. (James Wilson Bright Collection, 46005).