Hi Mark, can you tell us what exactly you are trying to do? If you want to save photos that you already have on another device (i.e. a computer) to the SD card, you can copy/paste them onto the SD card folder via file transfer. But if you want to save photos taken with the camera to the SD card, you just need to specify it through Settings.
Go to Settings > Storage > Default write disk and make sure that external storage or SD card is selected. This will ensure that all photos and downloads, even apps get stored on the SD card instead of the internal storage space. Hope this answered your question!