A literature review is an organized presentation of existing research on a subject. Depending upon the scope of the subject at hand, this can be a time-consuming task; however, the narrower the topic, the easier it is to know what to put into the literature review.
In this case, female oppression in dystopian literature—especially in The Handmaid's Tale—is a well-defined subject. Because it is specific, it should be easier to determine what goes into the review. The first thing to do would be to gather relevant writing on this subject. Using your university's library databases can be a big help: use search terms such as "female oppression," "The Handmaid's Tale," and "dystopian fiction" or "dystopian literature" to see what has been written on the subject over time. Since The Handmaid's Tale was published in the 1980s and turned into a popular TV series not that long ago, most writing on that book specifically will encompass the last three decades. Looking through books (usually critical anthologies) that feature relevant criticism of the novel might also be helpful.
As you read the relevant literature on the subject, note if thinking on the book's presentation of female oppression in a dystopian world has changed over time. What are the common ideas in the writings? Have certain interpretations been challenged or elaborated upon over time? It will probably be helpful to take notes on the readings so that it will be easier to synthesize the information into coherent commentary on how critics have approached the subject since the book came out.
Once you feel you have a significant amount of critical writings for your literature review, now it's time to put down how these critical writings approach the topic, noting any changes over time. Also see if the writings have any connections or overt references to one another. The point is to tell a story of sorts with the review, the story of how people have looked at your chosen subject over time.