With a citation generator, you can enter the bibliographic information of your source, in order to produce a citation in your selected format, that you can copy and paste into your paper.
Here is a selected list of citation generators:
Microsoft Word Professional offers an APA citation tool and some of the library databases offer APA citations. While they often contain all the elements for the citation, they are often not in correct APA style. Before relying on these citations, you will want to check with your APA manual, NoodleTools or the DU English Department's APA Documentation Style: A Brief Overview to make sure that your citation is correct.