Where there are one or two authors, include all authors in the in-text citation, for example:

Smith (1983) found that…

…as has been shown (James & Ryerson, 1983)…

If your reference has three or more authors, you can then use et al. (meaning ‘and others’) in your in-text citation, for example:

Research by Harrison et al. (2003) shows that…

For APA 7th, you need to record all authors in your final reference list or bibliography. You can only use et al. if there are more than 20 authors.