Your first stop for help with your writing here at USI should be the Tutoring programs in the Academic Skills department. You can schedule an appointment with a tutor or send your work to the Online Writing Lab for feedback from a writing consultant.
Your Liaison Librarian can also help you get started on the literature review process, as well as offering some assistance for correctly formatting your work and including correct citations.
The figure below is an adaptation of the levels of evidence as presented by Melnyk and Fineout-Overholt (2015, p.11). According to the authors, these levels should be viewed hierarchically in terms of objective reliability and generalizability; with Level I representing the most generalizable and objective evidence, and Level VII representing the least generalizable evidence with a greater risk of bias (p.92).
Levels of Evidence and PICOT charts adapted from:
Melnyk, B. Mazurek, & Fineout-Overholt, E. (2015). Evidence-based practice in nursing and healthcare: a guide to best practice. Third edition. Philadelphia: Wolters Kluwer Health