Encyclopedias provide background information on key concepts, events, places and people, making them an excellent place to start exploring a paper topic. In addition to general encyclopedias like the Encyclopaedia Britannica, the library has many other specialized encyclopedias about the World Wars and the historical events surrounding them.
Another good place to find encyclopedia articles online is Credo Reference. Below are some examples of very specialized encyclopedias for World War II.
Bibliographies and research handbooks can be a great help by pointing you to literature written and selected by World War scholars. Here are just a few examples.
The folks at the Cornell University Library have a nicely-written page: Introduction to Research.
This is a good page to review throughout your research project, and especially right at the beginning.