A more extensive guide to APA from Purdue's Online Writing Lab (OWL). You may need to click through the tabs on the left to find the information you need.
Publication Manual of the American Psychological Association
The APA 7th Edition is the complete manual for citing material and formatting your paper according to APA guidelines. The library has multiple copies on the bookshelf behind the Reference Desk. Spiral bound copies can be purchased online for around $40.