Science papers generally report the results of experiments in which a hypothesis states the intent of an experiment and whether the intent was proved or disproved. Humanities papers often present interpretation and criticism of original works. In any event your paper will include a hypothesis, argument, or statement of intent. I have collected all the background information I need to ask the right questions and formulate my arguments. If you have never heard of rotary engines, or know nothing about the salmon industry, gathering background information will be necessary.
Encyclopedias are always a good place to start.
Your professors may have mentioned that you should not use an encyclopedia to write your paper. This doesn't mean you shouldn't look at them at all. Reading an encyclopedia entry can help you become familiar enough with a topic to narrow it down. The other really important thing to remember about encyclopedias is that there are many kinds. Encyclopedia Britannica or the World Book are great places to start looking for information but if your topic is rotary engines don't forget to look for for an Encyclopedia of Science and Technology.