APA 6th EDITION (see left column) or APA 7th EDITION (see right column)
It may be difficult to position the page number and the running head on the first page and then format them differently on subsequent pages.
Watch all or part of this 18-minute YouTube video which explains how to set the format in Word using Windows. Here are the time segments in case you want to skip around the tutorial:
Source: Samuel Forlenza, published January 6, 2018 on YouTube.com
Tutorial by Terrance D. Jorgensen, Kennesaw State University, Kennesaw, GA demonstrating how to type a paper using APA format on a Mac computer.
This is a 10-min. video.
According to Fordham's Academic Honor Code, "plagiarism occurs when individuals attempt to present as their own what has come from another source. Plagiarism takes place whether such theft is accidental or deliberate. It is no defense to claim that one has 'forgotten' to document ideas or material taken from another source . . ."
Become familiar with the writing style guide suggested by your professor. Almost all subject areas have their own style guides. The more common styles are presented under the page "Citation/Documentation;" APA, MLA, and Chicago Manual of Style (CMS).