To cite an online lesson, follow the MLA format template. List the name of the instructor in the “Author” slot, the title of the lesson or a description of it, the course title, the sponsor of the course, the start and end dates of the course, and a URL:

Venard, Lourdes. Lesson on nominalizations, wordy language, and passive language. Copyediting: Intermediate, Editorial Freelancers Association, 5 June-17 July 2018, www.the-efa.org/product/
copyediting-intermediate-session-2-online-jun-5-jul-17. 

If you are citing supplementary material your instructor created for the lesson and uploaded to the lesson page, provide the the title of the supplement or a description of the material in the “Title of source” slot. For clarity, you might indicate the format of the supplement in the optional-element slot at the end of the entry: 

Venard, Lourdes. Nominalizations. Copyediting: Intermediate, Editorial Freelancers Association, 5 June-17 July 2018, www.the-efa.org/product/
copyediting-intermediate-session-2-online-jun-5-jul-17. PDF download.