Please check that the garment is clean before you commence your repair. Always use greaseproof/silicone paper on both sides of the repair where possible. Alternatively you can use ordinary writing paper if the fabric is not delicate.
Place your paper onto an ironing board. Turn the shirt inside out and place on top of the paper. Cut a piece of matching fabric to fill the hole with, from a concealed part of the garment like the collar, cuff, or somewhere where it will not be missed. If you cannot do this, cheat, and use a spare matching piece of fabric from another garment instead. Or you can purchase a small piece from a shop.
Remember you only need enough fabric to fill the hole so you are only looking for a tiny piece. So look twice because you will find enough fabric in 99.9% of most garments. You may wish to trim any frayed or burnt edges away first. Fill the hole with the fabric so that it fit the hole exactly.
Sprinkle the Supermend over the top of your filled hole, covering a slightly larger circumference area.
Place a backing patch on top of the powder. Hold down with fingers and blow away any excess powder.
Cut the backing patch a bit bigger than the hole.
Some tips on backing patches. You are going to make your own from a fabric with a similar texture to the one you are repairing. The reason for this is to keep your fabric repair soft. It does not have to be from the same fabric that you are repairing. You could use an old piece of handkerchief / bed sheet. Etc. For silk or chiffon shirts and blouses use stockings, tights, net curtains, netting or a fine nylon fabric. Or if you are lucky enough you can use another piece of fabric from a concealed part of the garment. That way you get an invisible repair both sides.
Now simply put your paper over the top and press with a full cotton temperature iron. If it is a fine fabric, use three to four layers of greaseproof/silicone paper on both sides. This will enables the safe use of a linen/cotton temperature setting.
Supermend will melt to fix all the fibres together and the job is done.
All effective repairs can be washed boiled and dry-cleaned, over and over again.