Can't Transfigure!

[Mack Whitman]

I just read up on Transfiguration so I bough the XL Edition of Carter's Display, filled it with 5 different cuts of gems (though only 4 different varieties of gems) and I figured I could try to transfigure them so that I can get the skull cut.  And what did I get?!  NOTHING!  I can't transfigure!  The only two options are "Add" which is blanked out since I have the display full, and "View" which only shows me the first gem I put up.  I assume that there's supposed to be something else I can do with it.  What am I doing wrong?