The history of psychology is a professional, scholarly field in its own right. A number of journals are devoted to it, among them The Journal of the History of the Behavioral Sciences, History of the Human Sciences, and Isis: A Journal of the History of Science Society.
In your manuscript, you need to situate your work historiographically, that is, explain its relationship to the existing scholarly literature on the topic. This is your opportunity to explain what new and original insights you are contributing to the historical understanding of your topic.
If historians have not treated your topic, explain why not and justify your attention to it. A manuscript that contains no historiography (i.e. no references to articles from History of Psychology and/or related historical journals) is unlikely to be published.