The Photos section of iExplorer is read-only and is only designed for transferring photos and videos to your computer. If you want to transfer them to your device, you would need to use iTunes Sync or you could transfer them to our free iExplorer Mobile app (in the App Store) which will let you move them to your Camera Roll from there. You just won't be able to go directly to Camera Roll with iExplorer. The way iOS works, you can add files to any directory, even the Camera Roll (Media/DCIM) directory, but that doesn't update the database on your device necessary for viewing a photo or video in the Photos or Videos app. If you use iExplorer Mobile, you can put the file(s) in its Documents folder, and then you'll be able to view the photos or videos within iExplorer Mobile on your device. Once it's in iExplorer Mobile, you can then save any photo or video to your Camera Roll (Photos app) as well as share files with your computer over WiFi. Here is more information about our free companion app iExplorer Mobile:
Once iExplorer Mobile is installed on your device, you can add any files to it by using iExplorer or iTunes File Sharing. To do it with iExplorer, just click on the iExplorer Mobile button on the Device Overview (Home) screen or go to the Apps section and open the iExplorer Mobile app folder from the alphabetical list. Then, open the Documents subfolder where you can add files or entire folders via drag/drop or right-click and choose Add Files. Any files you add to the Documents folder will appear in the iExplorer Mobile app on your device.
Once the photos or videos are in iExplorer Mobile, to then move them to your Camera Roll, just open iExplorer Mobile on your device, hold your finger on a photo or video file to select it. Then, tap on any other files you want to select and tap on the Share icon in the lower left corner (square with an up arrow) and choose "Save...". This will save all of the selected images or videos to your Camera Roll.
If you don't see a "Save..." option in the Share menu, then you most likely accidentally chose to not allow iExplorer Mobile access your Photos. To check and fix this, just tap Settings > Privacy > Photos and make sure the switch next to iExplorer is set to ON (green). If it is already set to ON, please try toggling the setting by tapping the switch to OFF and then tap again to turn it back ON. Then, check in iExplorer Mobile again. If you still don't see the Save option for photos or videos, please completely quit and close iExplorer Mobile and try again. To do this, just double tap on your Home button which will bring up a series of windows for all apps that are currently running on your device with the recents first and swipe up on iExplorer Mobile's window to fully close it. Then, reopen iExplorer Mobile and check again. If you still don't see the Save option, please tap on the 3 horizontal lines in the upper right corner of iExplorer Mobile and tap on “Import from Camera Roll” and see if it works by tapping on any photo which will show a red checkmark on it to indicate that it is selected and tap on Done in the upper right corner. Then, check your Documents folder in iExplorer Mobile for whether the photo appears. If it does, try the Share menu again, and you should see a Save choice which will make a copy of any selected file(s) in your Camera Roll.