Yes, you have to have a minimum of 2 years of critical care experience to sit for the test. You can always prepare in advance though, so you're ready to test right at the 2 year mark.
Having rhythms down is big. I strongly recommend a book called Rapid Interpretation of EKG's by Dr. Dale Dubin. It's an easy read with a full explanation of 12 lead interpretation.
Also, read up on STEMI, NSTEMI, a-fib, pacers (external, internal), AICD's, CHF, pulmonary hypertension, aortic aneurysm, aortic dissection, hypertensive urgency and hypertensive emergency.
Start with the rhythms and work on the other topics listed, in no particular order.
Best of luck and congrats!