Primary sources are documents produced at the time of the event you are studying. So, primary sources from the Revolutionary War would have been created during that time, and reflect the event in some way (speeches related to the war, journals and pamphlets, newspaper articles, diaries and letters written at that time, etc.). These can be difficult to use - not because they are hard to find, but rather because it is hard to find the right one that will illustrate your topic.
Also to remember: these documents reflect the biases and opinions of the author or creator. They are not neutral! For example, a newspaper might only publish sensational, exciting news to sell copies - it might not give a fair picture of the time period. You should always keep this in mind when using primary sources.
Luckily, because the study of war and military history is popular, there are a lot of collections available to view.
These are easy to find and contain reliable, quality resources. When searching full text, you must use the words of the TIME. For example, you cannot search WWI if looking for newspapers from that time - it was not called WWI until WWII happened! You'll have to try things like "Great War" or even just search "war" and use the time period limiters on the side.
There are too many open digital collections to include here; this is just a sample of what is out there! if you find a collection online, please check with your librarian or Dr. Kawamura to make sure that it is reliable and good for your topic. Here are a few larger collections; you can do searches within these to find more specific sources. Try to Google the name of the war and "digital collections" - and look for those housed at universities, libraries, or government and cultural institutions (not just some random blog or website!).