First, let us look at the equation itself:
In other words, The perimeter of the circle is equal to two times 3.14 times the radius of the circle (which is a line that starts at the circle's center, and ends where the circle ends). Now it should be easy to find the circumference from here.
For example, if the radius was 1, then the equation would be C=2*3.14*1, or C=2*3.14. Now, we times 2 by 3.14, and we get 6.28, and that is the circumference (roughly) of the circle.
Hope this helped!