A journal may require potential authors to follow APA style, AMA, another style, or their own. To find out what you need, perform a google search for the journal's title. Once at the journal's homepage, look for "for authors," "author guidelines," "submissions," or something similar.
Purdue Online Writing Lab APA Overview
On the left side, APA examples can be found under the heading Reference List. Reference List: Electronic Sources might be of particular use if you are having trouble citing something from the internet.
APA Style Guide at Central Library
BF76.7.P832010 (Floor 2: Reference). The library carries multiple copies.
APA Citation Examples from the UMUC Library