DOI stands for Digital Object Identifier. It is a unique alphanumeric string assigned to an article; think of it like an article's student ID. DOI is a more reliable way to link to articles than the URL, which can change.
The information that you need to correctly generate a citation, including the name of the database, should all be available on the detailed results page. If it is missing, you may need to do some sleuthing to find what you need. The librarians are happy to help with that!
If there is no DOI, you will need to use the URL for the article. To get a reliable URL, use the permalink option in the right column. This will generate a permanent URL that will show beneath the search boxes.
Finding citation information for articles that you found using another source, like Google Scholar, may be more complicated. It's important to remember that even if you found a scholarly article outside of the database, it should still be cited as an article, not a web page.
The title of the article and author(s) should be easy to find at the top of the page.
Other information may be more challenging, as there is no consistent place to find it. It will most likely be found at the top or bottom of the page. Information like volume and issue may not be on the pages themselves, but you should be able to find it on the journals website. If you're not sure, a librarian can help.