First, check your course syllabus and lessons (both are linked on the left side of your online classroom). Your instructor may have provided citations for your required readings in one or both of those places.
If you need to create a citation from scratch, use your style guide to help you.
Each style guide has a section titled "Citation Examples." Click the type of source you'll be citing to see examples of proper citations. For instance, if you need to cite a:
Lesson or lecture in your classroom: use the COURSE NOTES & LECTURES examples
Textbook or book chapter: use the BOOKS & BOOKS-ELECTRONIC examples
Article from a journal: use the JOURNAL ARTICLES examples