If you know where the article was published (i.e. in which journal), and when it was published, the Journals A-Z list is the fastest way to see if the article is available in the Sprague Library.
Many journals are not available through the web. This is because most journals charge for access to their articles. Since you're a student at Montclair State, the Library pays many of these costs through subscription fees. As such, most of the time you'll need to go through the library's website in order to access the article so the journal publisher knows that you are a student here.
The library subscribes to over 230 individual databases, all of which contain different journals and articles. The Journals A-Z List will tell you which database the journal you're looking for is in.