The better you understand your research assignment, the easier it will be to complete. Be sure to ask your instructor if there is anything you do not understand.
Understanding Writing Assignments from Purdue's Online Writing Lab (OWL) may help you to better understand what your professor wants. Also, check out the OWL's pages on common writing assignments.
For tips on writing other types of assignments, check out the Assignment Calculator from the University of Minnesota which covers:
This Brainstorm and Explore a Topic tutorial will help you work through the process of selecting a research topic.
from Clark College's IRIS: Information & Research Instruction Suite
To get a better idea of what kind of sources to use in your research, you can think of different types of sources and the information they provide as a pyramid.
By themselves, the individual blocks that make up a pyramid aren't very exciting, but together the result is an awesome structure. Likewise, one source is not enough to write a strong paper, but you can write a solid paper by synthesizing information gathered from a variety of sources.
It is always a good idea to check your assignment or with your instructor for the types of resources that are required for your paper or project.
Just like the lower levels of a pyramid require the most "foundational" stone blocks, the sources that have the most detailed information and have a wider time perspective are at the bottom of the information pyramid. Scholarly articles and books take the longest to read but are the most detailed, while magazines, newspapers, television programs, and online sources are often the fastest to read but may contain less specific information and a more general overview.