To find primary and secondary materials in the library catalog, Prospector, and WorldCat, start by searching keywords that describe your topic.  For example, if you are researching colonialism and the Middle East, your keywords could be "middle east" colonial* british to begin your search (putting Middle East in quotation marks to find the exact phrase, and truncating colonial* with an asterisk to find the stem of the world and variant endings: colonial, colonialism).  For example, in Compass Search All:

If you want to refine your search, on the results page you can limit by "Archival Materials in Databases" or by "Databases," and you will find primary sources such as Confidential Print: Middle East 1812-1969 from the British Foreign Office:

Most history books will be secondary sources, but check the "Finding Primary Sources" tab for suggested strategies for finding primary source materials in the library catalog.