It really is just generic help, I got it, now what do I do with it? I've downloaded what I believe to be the latest firmware, put an .nds file in the root folder, and it doesn't run. I hit A, I click on it, and it doesn't respond. It might just be bad, I don't know. But the tutorials I'm seeing online don't exactly sound reliable, either. Could someone give me a rundown?

Which M3DS are you using? Get G6 and M3 Real latest here.

http://www.handheldsources.com/M3DS/Download_M3DSR.html

Also don't put roms in the root. Put them in NDS folder.

which M3 cart we're talking here? M3 Simply or M3 Real?

first of all, format your microSD to FAT/16, then install firmware.
if it's M3 simply then all you need is install the full firmware pack, the latest is 1.14 (http://gbatemp.net/index.php?download=2310).

Unrar it to the main dir. Make a new folder call Game or whatever you like to call it, put all the .nds there. Unplug then just access the game folder, then select your .nds and ye good to go.

I'm using the Real, I got the system from that very sight earlier today. I didn't have the things in an nds folder at first, but now they're in there with the same result. Should the nds folder be in the root folder or the system folder?

Doesn't matter- you can boot roms from any location. I was just thinking maybe there was a problem booting from the root or something.

I can't format to FAT/16, I can only select 32.

Okay, maybe I'm stupid. It was the firmware messing up, I redownloaded it and it works now. Thanks for the help.

???

Are you on XP? Vista? AFAIK, I do remember seeing an option to format the card FAT, FAT32. FAT16 is FAT btw.