All of these guides are from the Online Writing Lab (OWL) at Purdue.
Footnotes are a way of giving credit to your sources. Each one points from your text to an entry in your bibliography.
To insert a footnote in Word:
Never created an annotated bibliography before? Check out this guide from the OWL at Purdue.
The University of British Columbia Library has a good visual depiction of how to write a good evaluative annotation.