Give the full secondary source citation in your references list. Let's say this is that source:
Coltheart, M., Curtis, B., Atkins, P., & Haller, M. (1993). Models of reading aloud: Dual-route and parallel-distributed-processing approaches. Psychological Review, 100, 589-608.
For your in-text citation, name the original work and also give a citation for the secondary source. For example, if Seidenberg and McClelland's work is cited in Coltheart et al., use the following in-text citation:
In Seidenberg and McClelland's study (as cited in Coltheart, Curtis, Atkins, & Haller, 1993), it was found that...