This 4-part How PubMed Works series from the National Network of Libraries of Medicine (NNLM) offers a tour of the features of PubMed.
Videos are between 60 and 90 minutes each and offer an in-depth introduction to searching in PubMed.
*The above tutorial recommends checking the Full Text limiter. If you want to see all of the articles on your topic that are indexed in CINAHL, not just the subset of indexed articles with full text available in CINAHL, you will not want to check the Full Text limiter box.*