If you are going to a decent school, they will have some sort of library for you to use -- maybe even a research lilbrarian to help you. Check out your school's resources first. You are already paying for them. I am often amazed how often students are unaware of the resources available to them. Your instructor should also be able to point you in the direction of your school's library resources.
Free resources available to the general public (such a Google, Google Scholar, Medline, PubMed, the Cochrane Collaboration, the JoAnna Briggs Institute, etc.) can be helpful, but are limited in what they have to offer. The best resources is a good university library with access to all types of information, including the professional nursing journals.