Assuming you use a .3ds/.3dz and not a CIA: Basically you load SDF, hit home, pick ORAS from your gateway ROM list, go back into SDF, then where it says CTR CARD, you press X to extract the save to your 3DS's SD card. After that, you can either turn off the 3DS and connect the SD card to your computer, or use ftpony/ftbrony to move the game's "main" file over to your PC and edit it, then put it back. After that, go back into SDF and re-import it.
If you're using a CIA of ORAS, just load SDF via gateway or a CIA, then export your save, edit it, and re-import it (same as above, use ftpony/ftbrony or just move the sd to your PC).
Not exactly a step by step, but using SDF isn't really rocket science. If you need more help, just post back..
Also, to delete your save, boot ORAS holding up + B + x.