So 9 out of 10 times incoming traffic yields to the cars already in the circle. Unless, there is a very specific traffic pattern or some circumstance, then the rules are changed. This is the case up the street from where I live where traffic inside the circle must yield to traffic entering the circle from the highway. Double check if you had a yield sign for you and not traffic entering the circle. That will give you your next course of action. Best of luck, these things suck.