Instructors are the final authority on how they would like you to cite your work. Librarians will refer to the established handbooks when necessary to determine how to cite a particular resource.
Library databases provide a citation for each source that you can copy and paste into your reference list. If you find a source on the internet, you will have to create a citation by looking for the needed information.
Never assume you will get a perfect citation from citation generators or library databases. They will usually include most of the information needed, but spacing, punctuation, and capitalization tend to need corrections.
Click through the slides below to see examples of where you can find citations in various library databases.