I found a nice guide: http://www.n3dscart.com/pages/R4i%252dGold-Setup.html
I think I need this firmware but all links are broken http://www.r4i-gold.me/en/download/skin/2012/0115/281.html
They also didn't work. I downloaded the latest edit of the orignal R4 Firmware from r4li.com. On my DS Lite I got a loading screen, but its stuck there.