Install tool of your choice in spindle, record diameter first.
Touch the tool to the side of your work in X, hit "zero" X.
" " Y hit "zero" Y
" " Z hit'zero" Z
Lift the Z clear of the work. Hit go to zero.
In MDI type X (1/2 diameter of tool), Y (1/2 diameter of tool) "enter"
Machine will now move tool to the new 0,0,0,
"Zero the X and Y. (Z is already correct) The theoretical tool center is now over the corner of your work.