There are two useful methods of transfering the desired image to the copper plate: Photo exposure
or direct toner transfer, which saw as the easier ( but maybe more inaccurate ) method i will describe now.
Before continuing, we have to clean the surface of our copper thoroughly, using rubbing alcohol or other good cleaner. No spot of whatever may be left before the transfer.
Now we need a negative of the image we want to etch. You need to print that on a as glossy as possible sheet of paper. You have to experiment a bit. I chose photo paper for inkjet printers, but i read, that also pages from product catalogs are good. You need a paper, which has a very flat surface so the toner cannot stick to it too good.
Use your iron at a high temperature to first heat up the copper. Then put the sheet with the print towards the copper on the plate and apply it with high pressure of the iron. Take care not to move the sheet or the picture will be messed up. How long you have to press them together depends on the materials used. Again. a bit experimenting is neccessary.
When the sheet is stuck on the plate, put i in hot water for some minutes, until the paper just comes off. After a bit of soft rubbing, the paper should come of completely and only the toner remains.
That was the tricky part...