You can use either a shadow area or a highlight for determining exposure; you may want to have reference knob settings for each as some images have interest in the highlights and some have their interest in the shadows.

You can use the meter to find a negative's contrast by first zeroing the lens' aperture on the shadows and then turning the EM-10 knob for the highlights. You can then use the highlight reading to determine, at a first try, a paper grade for the negative.

A step tablet can be a great help with an EM-10: printing the wedge will give you the paper's range; taking readings of each step will let you relate knob reading with the resulting grey tone on the print. You can make a rough calibration for your meter by zeroing the meter with the lens one stop down from full open and then noting the knob settings as you zero the meter as you stop the lens down. Don't start at full open - full open is always optimistic and an "f2.8" lens may actually be f3.3 when wide open.

EM-10's are not calibrated and one person's knob reading -> density chart won't necessarily work with your meter.

The Darkroom Automation meter manual may aid you in using your EM-10.