Learn the basics of constructing reliable and accurate searches in this video tutorial from PubMed, a database of Health Sciences citations maintained by the National Library of Medicine.
Summon Discover is the library's tool that searches acros databases (including MEDLINE and CINAHL), electronic books, and print books at the same time. You can access it at https://pacollege.summon.serialssolutions.com/#!/.
This video from the EBSCO database CINAHL also introduces fundamental search strategies, with a focus on using subject headings and controlled vocabulary to narrow your search results. All databases produced by EBSCO follow the same basic searching layout.
This PubMed video takes a closer look at identifying useful search terms and introduces MeSH (Medical Subject Headings), the hierarchy of controlled vocabulary used to index subjects in PubMed.