When you're looking for scholarly sources in history, it's essential to check the relevant database(s) to find journal articles. Use America, History and Life when you're researching topics that involve the US. Use Historical Abstracts for researching topics beyond the US. It's often a good idea to check both if you're researching something with an international component.
Use the FindIt button to connect with the full-text PDF (or to request the article via ILL).
In terms of actually finding articles related to the topic(s) you're interested in, think about the terms scholars use to refer to your topic. If you find some articles that (at least vaguely) relate to your topic, look at the Subject terms applied to them. Then try searching for those subject terms (change the drop-down menu to "SU:" or "DESCRIPTORS," depending on the database you're working in.
On the Advanced Search page of both Historical Abstracts and America, History and Life, you can narrow your search results to articles discussing particular time periods. This can be helpful to narrow down your results.