Your information need will determine what type of source you consult for research. Two broad areas of materials are primary and secondary sources. Primary sources are first-hand accounts like diaries or letters composed by someone who actually experienced the event.
Secondary sources are interpretations of those events such as criticisms or newspaper articles which are written by someone else.
Below are two good websites filled with primary sources for historical or period research.
Your instructor may require you to use scholarly or peer-reviewed sources. Scholarly sources are written by experts in a particular field. They cite their sources through footnotes and bibliographies. Non-scholarly sources are works which are considered popular or more for entertainment than serious research.
Your instructor may require that you not use "popular" or non-scholarly works in your research. Which of these would be considered "popular" and which is "scholarly"?