First, make or get a DreamPi. Then make sure your image follows this criteria: http://jetgrindradio.dreampipe.net/imagecreation.html
To access the in game browser, go to the doghouse/internet and then drag mouse to very bottom of screen and you have to hold A and press start 9 times and then press Y (I mashed in frustration 2x and this is all I can say)
Then save the image by pressing X and A simultaneously.
Select "DL" from the list.
And that's it.
Xiden pretty much explained it from start to finish over here: viewtopic.php?f=42&t=11623
Post your art here: viewtopic.php?f=2&t=11765