You reference according to APA style by citing the author/authors and year of publication, i.e. the information you then put in first and second place in your reference list. This makes it easy for the readers to know where they should look for the complete reference to a specific source in the alphabetical reference list.
For the in-text citation, cite only surname(s) and year, even if the reference list entry contains a more specific date. Use "n.d." (no date) for references with no date.
There are two different ways to create in-text citations according to APA style; parenthetical and narrative. You choose what fits better in your text and you can use both alternatives in the same text. Using both ways is also a way to vary your text. However, make sure there is no confusion as to what citations are connected with the different paraphrases of your text. Also, do not use narrative and parenthetical citations in the same sentence.
Parenthetical citation is when the whole citation appears in paratheses. If you include more than one sentence for the same citation, make sure the citation comes at the end.
The marine animals that inhabit tide pools enjoy swimming (Doe, 2018).
Narrative citation is when you incorporate the citation as a part of the sentence. The author appears in the running text and the year in parentheses immediately after the author name. Use narrative citation when you want to highlight the author for some reason, for example when you refer to two authors who agree with each other or have different opinions. It is also appropriate to use narrative citation if the paraphrase is long, in order to clarify where the information comes from.
Doe (2018) studied the swimming habits of marine animals in tide pools.