Cite the first author plus “et al.” in every in-text citation; include all author names only in cases where "et al." is not enough information to identify which author in the references the citation refers to, such as duplicate citations for two different groups of authors (e.g., two resources with distinct authors share the citation "Patterson et al.").
American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). https://doi.org/10.1037/0000165-000