If you are citing from an edited work then you first need to check that there is no specified author for the part of the work you are citing. If there is, then you should follow the guidelines for referring to a chapter in an edited book.
If no such acknowledgement exists, then you may assume that the editor is the originator of the text. The editor's name is then used in place of the author's name in your citation:
Dewey's (2003) guide to canine and feline neurology provides the clinician with everything necessary for accurate diagnosis of neurological disease.
In the reference list the editor's name is followed by the abbreviation (ed.), like so:
Dewey, C.W. (ed.) (2003) A practical guide to canine and feline neurology. Ames: Iowa State Press.
Multiple editors: Where a work has more than one editor their names are cited and referenced in the same way as multiple authors. The suffix (eds.) should be included after the last editor's name in the reference.