To measure from point to point click the left point and then click the right point and a box will appear stretching from point to point. If this is correct then click submit measurement or click again to cancel and start again.

HINT Don't forget if you are on a tablet then you can stretch the screen to make the image bigger and easier to work on

Measure from cheekbone to opposite cheekbone.
On top of your cheeks below your eye level with the bridge of your nose.