Jolene
If it is the same exam simulator that i got from the Prepcast site, then you can take Quizzes, and full test exams. I remember you when you take quizzes you can decide on the number of questions you want to take for that quiz. What I do not remember is if you can choose the KA you want to focus on. The simulator does provide analytics after each quiz and exam around the KA and how you did.
When I prepared, I did 4 full exams and many quizzes of various lengths. I always reviewed the questions at the end of each quiz or practice exam and plotted the KA's I needed to review. About a month out, I took a 20 question quiz every day just to get my head around the question format and I think that is what helped me the most. I would take them during lunch at work and review them at night in more detail. If I was low in an area, or if a question stumped me I took out my Rita book and the PMBOK to review the topic.
I hope the helps!
Kevin