Save your creation
Right click the image on your left and select "Save image as..." to download the card on your hard drive. Take care to use a directory that you can easily remember (your desktop for example).
Insert the image in your word processor
Launch your word processor (OpenOffice, Word, ...). Into a new document, Insert your image (Insert -> Picture -> From file).
Ajust image size to fit a pokémon card
The image is bigger than a pokémon card. So you need to reduce the image size to fit to a real card. The size of a real card pokémon is 6.3 cm x 8.8 cm. You just need to adjust the width of picture to 6.3 cm.
Double click on your image. Take care that the "Proportional" box is checked so the height is automatically adjusting to the width. Enter 6.3 cm width and valid.
Print your card and glue on a real pokémon card
Now it’s time to print the page with a color printer, to carefully cut your card and to glue it on the back of a real pokémon card (a doubles card that you can sacrifice).
It’s done, you have a completely customized pokémon card!