I know you have the best intentions but why do people always tell applicants that the best advice is to be yourself? That's just so generic and unhelpful.
The test screens for personal and professional characteristics and then ranks applicants based on your score so unless you are a natural, you are going to have to work on improving how to put your best foot forward and how to shape your "personal and professional" characteristics answers to maximize your performance. How do you do that?
1) Read the liteature on situational judgment tests
2) Read about how they can be faked and shape your answers
3) Practice with sample questions from reliable sources especially on behavior descriptive.
4) Get feedback from ppl who know what the heck they are doing and who can be very critical of you. You won't benefit from a friend who is always "nice" even if they are in med school.