Below you can find several guides on searching in PubMed, both by PubMed itself an by other institutions.
There are notable differences between guides of different organisations that are based on the way in which assignments are graded. Keep these in mind when reviewing material from other institutions.
Librarian Carey Price Youtube channel with various database-related tutorials.
Through this link you can find self study modules and a libguide with information about PubMed.