im assuming you mean show the peak to peak value on the screen between the two cursors?
under the 10X mag button the one to the left is the delta Volts button... press that down and you will get a voltage readout on your screen..
make sure your intensity knob is turned clockwise... otherwise the scale factors wont display..
I dont think yours has an auto measure thing though... all you can do is position the cursors... its handy but I find a DMM much quicker and accurate..