APA (see APA, section 8.6, p. 258) defines a secondary source as content that has been first reported in another source. APA recommends that secondary sources should be used only when the primary source is unavailable and that you find the primary source and read it for yourself. However, there are instances in which the original source is:
In these cases, you would list the secondary source in the reference list, name the original work and use an in-text citation for the secondary source.
When citing a secondary source, provide a reference list entry for the secondary source. In the text, identify the primary source and then write "as cited in", name of secondary source. If you know the publication year, add that to the in-text citation.
This example is from the APA manual, p. 258
(Rabbitt, 1982, as cited in Lyon et al., 2014).