When you add a photo to Smilebox, it is automatically stored in your Photo Gallery. If you want to use it for other creations, you can find it by clicking + Add photos in the editor.
If you click on Add from My Gallery, all your uploaded photos will appear.
If you want to remove photos from the photo gallery you will need to use the extension myfiles at the end of the Smilebox URL.
Or just copy and paste this URL to your browser:
From here you can delete photos, one at a time. Select the photo you would like to delete by clicking it.
It will open up in a new screen, where you can click Delete at the top of the screen.
This will remove it completely from your account.