if I remember correctly, just drag the shape onto your page and do a copy
paste and the pasted item will be in the center of your view...so first zoom
to "fit page to screen", then "paste" (delete shape you "copied" if no
longer needed).
Of course placing a vertical and a horizontal ruler guide, crossing at page
center...then drag shape and let it snap to guides works well too and
provides a lasting reference.
Doug.S