Scenario: You read a 2007 article by Linhares and Brum that cites an earlier article, by Klein. You want to cite Klein's article, but you have not read Klein's article itself.
Reference list citation
Linhares, A., & Brum, P. (2007). Understanding our understanding of strategic scenarios: What role do chunks play? Cognitive Science, 31(6), 989-1007. https://doi.org/doi:10.1080/03640210701703725
Your Reference list will contain the article you read, by Linhares and Brum. Your Reference list will NOT contain a citation for Klein's article.
In-text citation
Klein's study (as cited in Linhares & Brum, 2007) found that...
Your in-text citation gives credit to Klein and shows the source in which you found Klein's ideas.