The Johns Hopkins worksheets and developing a PICO question supply the framework for research and enquiry. You will want to formulate your question in order to develop a search strategy.
PubMed or CINAHL are common starting database for health sciences literature reviews, and for some projects, will provide enough journal articles. (Pubmed or MEDLINE (Ovid) are different interfaces to the same content so searching both is unnecessary.)
No database includes all journals in a subject areas. If you are unable to find relevant materials in PubMed or, your question focuses on specific aspects of health sciences, you may want to use another database in addition to PubMed. See common sources for health sciences-related questions above; review the A-Z list of databases to see more; or ask a librarian.