Primary sources are first-hand accounts of an event or person. They are created during the time that the event occurred or when that person lived. Examples: autobiographies, diaries, film or video footage, manuscripts, artifacts, oral histories, audio recordings, interviews, speeches, letters, lab reports, photographs, and any of the above reprinted in the original format and language.
There are various places where you can search for primary sources. One is in periodicals--just click on the "Periodicals" button on the left! Another is an archives. Many prominent archives have their collections digitized and readily available online for your use. Archives are usually part of an organization: a library; club; institution of higher education; government; museum; and so forth. By seeking out one of these organizations, or combining their name with "archives" in a web search, you will find their archives website. (A good example of how to do this is by placing "Smithsonian" and "archives" in your Google search bar. The first hit will be the Smithsonian Institution Archives!)