The References tab allows you to add your citation information for your sources into your Word document. You select your citation style and Manage Sources to add each source. Select the type of source (Book, Article, Website, etc.) then type in all of the required information.
When you're ready, you can generate a Bibliography (choose Bibliography -> Insert Bibliography rather than selecting a preformatted option) and your Works Cited/References/Bibliography will be created.

You can use Insert Citation (once you put all your sources in) to insert an in-text citation and Insert Footnote to add a footnote.