How do I build literature critics in my exam answer?

The best way to think about literature critics is as an "expert opinion" that you can use to support your point or you can challenge to make a counter-point. In an exam, when you're feeling under time pressure or might be a bit worried about essay structure, you can build critical opinion into the basic PEE structure (point, evidence, explanation).

SO.. make your point (P), use some evidence from the text (E), explain the point in more detail (E), focussing on the language, sturcture, meter, semantics etc, and then use a critical opinion linking back to the orignial point- it can be  used to make a much wider supporting point, OR you can use the ciritc to show an opposing view.

By following a clear sturctutre you will be in the best position to create a clear argument and show case your knowledge in the exam!