Depends on your method of acquiring the information. If you used google scholar as mentioned above, it will be located below it. Also you can check online resources for citing:
From the APA: https://apastyle.apa.org/style-grammar-guidelines/references/examples
Another good resource: https://www.mendeley.com/guides/apa-citation-guide
That will give you some examples and rules to follow. If you're in a crunch, you can use a website to format the citation for you, but beware as not all of them may use proper format or the latest edition. Some options are:
Also, you can use applications to help with citations, like: Mendeley, which is an application you download onto your computer and will scan the PDF and create a citation. However, it may suffer from some of the same problems as the website based applications.