For class you should watch the first 13 minutes of the lecture below by John Rogers from Yale University that introducing Milton. You should also read the five sonnets (On Shakespeare, Sonnets 13, 18, 19, 23) and first 26 lines of Paradise Lost found here: Milton Sonnets. The introductions and notes to each poem will help you make sense of them, and you should focus especially on Sonnets 13 and 19 and the opening to Paradise Lost.

Listen from the beginning to timestamp 13:02.