I bought some from japancrafts.com.au . Their web site has a page that gives instructions for applying the transfers. They worked fairly well for me, but I have made only limited use of them and on very small dry pressed wares that were bisque fired to only a quite fragile state. The seller above recommended 1100-1300 C firing.
Dampen the ware with a lightly dampened sponge, apply the transfer, smooth down with a lightly dampened sponge, wait 2-3 minutes then cautiously peel the paper, laying it back down and sponging again if the color is not completely transferring. Too much water will dissolve and run the color.
I read somewhere that these transfers may have a limited shelf life.
There is video online showing similar transfers being printed in China. They were printed by intaglio from metal plates on small hand presses in a very rudimentary workshop.