1)Place the paper ink side down. Remeber to print it mirror image.
2)Iron it a little so that it takes to the surface a little, I've only done this with wood so it may work differently with other materials, we will be placing the cotton down in the next step so we want to have the paper stick in place, avoiding it slipping around once we're ironing the cotton.
3)Place the cotton sheet on the paper and place the iron down without sliding it. Apply moderate pressure and repeat until you have covered the entire image.
3.1) Repeat with more and more pressure, you can lift the sheet to check out progress. Once it seems like the paper is completely adhered to the surface you can iron directly on to the paper until it starts to discolour and/or become very shinny and smooth.
Its hard to over-do it but you can cause discolouration of the wood with too much heat and a little bleeding of the ink.
The whole process for an a4 sized transfer is about 10-15 minutes.