Instructions for iPad use:
1. Select the opacity level (100%, 50%, 25%) beneath the picture you desire.
2. Push and hold on image, then select 'Save Image'.
3. Open your iPhotos app on iPad and select the image you chose.
4. Tap image and press this icon located in the top right corner.
5. Select 'Use as Wallpaper' then press 'Set Both' located in the top right corner.