Secondary referencing is where you reference a source that itself is referenced in a source that you consult. For example, you find an article by Murphy (2022) who references an article by Kelly (2021) that says something interesting which you want to use in your work. You can't find Kelly's 2021 article, so how do you reference it? To do this, in your work, you'd say something like :
Kelly (2021, cited in Murphy 2022) said something interesting
or
Something interesting (Kelly 2021, cited in Murphy 2022).
Murphy (2022) is a primary source - one you actually looked at.
Kelly (2021) is a secondary source - one that you didn't look at, but was referenced in article that you did look at
In your reference list, you only need to reference Murphy (2022) because this was the article that you looked at, not Kelly 2021.
