Press TAB to get out of the Edit mode.
(if you don't leave the edit mode then when you move the Circle
the Pivot point of the object doesn't move with it )
Little explaination for the people who don't know what a pivot point is yet.
A Pivot point is an offset position (or better said a middle point)  for the object.. out of the edit mode it
will rotate,scale,move arround & with that point, as you don't use the Cursor as rotation/ move/scale point.

Press G to move the Circle.

Move the Circle just under the camera view.
Press 0 for the camera view.
So we get a nice full screen of fire after all settings are done ;)