Image formation for concave mirror when object is at centre of curvature

Think of the concave mirror as a parabola and the focus of the mirror as the focus of the parabola. Now from $2F$, draw an object of whatever height you want and draw a line parallel to the x-axis, namely $OA$. Wherever this line intersects the parabola say $A$, draw a line from this point and the focus and name this line $AF$. Draw another line passing from the object passing through the focus, $OF$. Wherever this line intersects the parabola, draw say $B$, draw a line from $B$ parallel to the X -axis and you'll get the image at the intersection of these lines which will be at a distance of $2F$ For an accurate image which you wanted you could refer to this : https://www.physicsclassroom.com/mmedia/optics/rdcmb.cfm