Yes, take off your SD card from 3DS; inject it into your computer. Drag and drop the 3DS ROM that you want to put on card or copy paste it. Eject you SD card from computer. Now your ROM is on your SD card.
Yes, take off your SD card from 3DS; inject it into your computer. Drag and drop the 3DS ROM that you want to put on card or copy paste it. Eject you SD card from computer. Now your ROM is on your SD card.