Click the 'Draw Circle' button which is located on the DRAW ribbon.
Move the cursor to where you want the centre of the circle to be, click on that point then move your mouse outwards to start drawing the circle. A line shows the radius of the circle as it's drawn, this can be X-Y coordinates (press F8 to select that) or Snap (press F7 to select that).
Click with your mouse again when the circle is the correct size to finish drawing it. The circle will have a red node when selected so you can move it but the size is not adjustable once it is drawn.