Author Last Name, Author’s Initials. (Date). Title of PowerPoint [PowerPoint slides]. Publisher. URL
Blanke, J. (n.d.). Bluebook citation [PowerPoint slides]. Mercer University. http://ssbea.mercer.edu/blanke/BluebookCitation.ppt
If the PowerPoint slides come from an online classroom or other online learning platform that requires a login to access, use the login page URL for the online classroom or other platform.