I don't know a video tutorial, but it's pretty easy to use.
You need to supply it a monochrome (grayscale) image. If you shoot with a color camera, you need to extract the luminance from the debayered image. Easiest way to produce that is to use the ChannelExtraction process to get the L component of the Lab color space.
Once inside the FWHMeccentricity script, select the view of your image from the dropdown and hit 'Measure'. It outputs FWHM and Eccentricity as the two most interesting parameters. Plus some standard deviations. The FWHM is in pixels - you need to know your image scale in arcseconds/px to translate that into arcseconds. Eccentricity is tricky in detail, but in general if it's above 0.7 then the stars are egg-shaped, Below 0.45 is perfectly round and everything in between is a matter if your personal taste. I am happy with everything below 0.6.
If you want to see the maps showing the distribution of values across your image, you need to click 'Support'. If you have too few stars then this part might not work.
I hope this helps you.
