Your own personal notes from a professor's lecture are considered personal communication. Therefore, they do not appear in the References list, and are referred to in the body of the paper only. Put the citation right after the paraphrase or quote from the lecture notes.
General Format:
(First initial of the person who gave the lecture. Lastname, personal communication, Month Day, Year lecture took place).
If the slides come from a course website, learning management system (e.g., CourseLink), and you are writing for an audience with access to that resource, provide the name of the site and its URL (use the login page URL for sites requiring login).
General Format:
Instructor's Last Name, First Initial. (Year Presentation was created). Title of presentation [Format]. Publisher. URL
Smith, G. (2019). Ownership structures in mass communications [PowerPoint Slides]. CourseLink. http://www.onlineguelphhumber.ca/
In-text citation:
Direct Quote: (Smith, 2019, slide 6)
Paraphrase: (Smith, 2019)
When the slides are available online to anyone, provide the website name on which they are provided, followed by the URL.
Smith, G. (2019). Ownership structures in mass communications [PowerPoint Slides]. SlideShare. https://www.slideshare.net/hellojenjones/guided-reading-making-the-most-of-it
In-text citation:
Direct Quote: (Nepean, 2015, slide 6)
Paraphrase: (Nepean, 2015)