Hi Laura,

Thank you for your question. Although i have not used to sharpen hairdressing scissors before its the same process as sharpening shears.

open up the handles so the edges of the blades are exposed and run the file a few times up and down the edge at the same angle as the original, normally about 30 degrees. Wear gloves as a precaution in case to prevent cutting yourself on the freshly sharpened edge.  You should see a bright new metal surface from the diamond file