My professor told me to find an article from a journal. How do I do that?

You can limit your search to professional journals in an article database by checking the box "peer reviewed". A peer-reviewed journal has articles that have been reviewed by a panel of experts before the article is published. This review process ensures that the article is of very high quality. Not all journals are peer-reviewed, however. Ask your instructor if he/she requires peer-reviewed journals for your research project.