Assuming you have one of the newer kernels, just open up your memory and get to [drive]:\_system_\themes\. Copy the theme files into one of the theme## folders and overwrite whatever's already inside and you're done.
Pressing select on the main menu will toggle among the 12 theme folders.
Do not rename the themes folders in the _system_ folder. Maximum is 12 themes. Uh, and make sure that the images are named logo, icons, background 1 and background 2, all 24-bit bitmap.
You'll need a file called CHEAT.DAT or USRCHEAT.DAT (caps)
But more importantly, you need CHEAT.DAT. You can get the best CHEAT.DATs from Rayder, a member in this forum (the link is in his sig)
Hold on a min, I'll go find his sig
EDIT: Its in here
EDIT 2: Oh yeah, put the CHEAT.DAT file in _system_
I think I saw on NDSThemes forums , something about making all the :
system
monshl
ebook(in system)
themes(in system)
cheat.dat(in system)
gbaframe.bmp(in system)
And all the files on themes and in every folder in themes..
Making all of them on caps helps the R4DS Function better with the skins..
^ Uh, no, not necessarily. Mine works fine with normal caps and lower case
And there are tutorials everywhere that show you how to make your own skins. And yet again, I'm forced to put up this link here. Skin making app. This is one of the best, IMO. So easy to use, and your skins look good. Or this one. R4 Theme Creator Alice. Yet another good one, and both are right from GBAtemp, not ndsthemes.