Wikipedia:Wiki Ed/tour/citing sources3

Position your cursor at the end of the first sentence (right after the period) and then click Cite. You can automatically add the journal article citation with either the URL — http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0184311 — or the DOI — 10.1371/journal.pone.0184311. (If it was a book, you could use the ISBN.)

Once you've inserted the citation, publish the changes.