How can i get the usb to work on softmii???

I've beeb trying for a week now and i still can't seem to get it working. i have system menu 3.2u with softmii, awith preloader
i put the folders on the sd an i still can't get it to show let alone being able to install the ios can some help with a guide for dummies.

Did you rename the .dol files to boot.dol?
The folders are in an "app" folder?