Historians rely on primary and secondary sources when conducting research and writing historical works. They also use qualitative and/or quantitative research methods to support their arguments and conclusions.
Here are some sources about research design and writing:
Wayne C. Booth. The Craft of Research. 3rd Ed. Chicago Guides to Writing, Editing, and Publishing. (University of Chicago Press, 2008) 0226065669 (available as a library e-book)
Jack Dougherty & Kristen Nawrotzki. Writing History in the Digital Age. University of Michigan Press, 2013). Open source e-book: https://www.jstor.org/stable/j.ctv65sx57
Provides complete full-text access to the 15th and 16th editions of The Chicago Manual of Style as well as the Chicago Style Q&A. Also provides access to the Chicago-Style Citation Quick Guide for examples of how to use Chicago-style citation.