Here's a quick step-by-step guide:
https://sites.google.com/site/mangao.../home/tutorial
It's quicker than it looks after you do it a couple of times and get the hang of it, i swear it >_>
Like i said, it's completely optional, you could simply rename your files to cbr/cbz and be done with it, but better safe than sorry, IMO. That method doesn't changes the image files in any way, the Aura HD handles images splendidly, there's no need to resize or alter quality. I do like to rotate all landscape images before creating the cbr/cbz but that's because i'm lazy and it's handier to rotate the Aura than going through the menu to rotate an image.