A thorough explanation of APA format may be found in the Publication Manual of the American Psychological Association. If you expect to be writing many papers in APA format, you may wish to purchase a copy for your own reference. More information about the APA Publication Manual can be found here: https://apastyle.apa.org/products/publication-manual-7th-edition
*Many counterfeit copies of the 7th ed. have been reported. Here's where you can check to verify you copy is official: https://bit.ly/APA7_Verify