First - Why do you have to cite in the first place? North Carolina State University has created this great introduction.
Penn State University Libraries, along with other institutions, has created guides to help you with the citation process.
There are several copies of the physical APA manual in the library.
Even if you find a scholarly journal or a newspaper article online make sure that you follow the guidelines for an ONLINE OR ELECTRONIC ARTICLE, including the addition of the DOI (Digital Object Identifier).
If you source is a website, make sure you provide more than just a VALID link to the site. You want to be sure that your readers can track down the site even if the link becomes broken.