These are several selected concise guides, available for download from the APA Style website.
The American Psychological Association maintains a website with a number of helpful resources about the details of writing in APA 7th edition style.
Another resource with a lot of great information about writing in APA and other common styles is Purdue University's Online Writing Lab (OWL).
Citation software can make the job of formatting and saving information about the resources you're using in your research and writing much easier. XU's Digital Initiatives Librarian, Leslie Whitford, created a helpful LibGuide with lots of details on installing and using Zotero, a popular free program for collecting and using citations.