To place the monogram in the top center of the wrist, start 1" from the center of the cuff toward the buttonhole and 1/4" to 1/2" above cuff edge. The bottom of the letters should fall at the bottom of the cuff. ;)
Here are instructions about placement of designs.
Hope this helps.
Never done them but would say on the buttom hole side bottom, as center wouldn't show it would be under the wrist..do a google for mongramed shirts embroidery and you will probably see some ideas... have fun *4U