Below are instructional videos on how to use a diamond sharpener. There are many other ways of course and in all honesty it doesn’t really matter that much because with practice all methods work more or less equally well. A common question is whether you should us the sharpeners wet or dry and again, with a diamond sharpener this is a matter of taste, but rinsing the sharpener after use prevents the resulting muck to settle between the diamonds and eventually make them not stick out as intended. Dishing the sharpeners with detergent, warm water and a dish brush also helps restore the health of your sharpener and prolong it’s life.
About the sharpening itself: Finding and maintaining the sharpening angle while grinding is key. It’s not hard to learn but still needs some practice.