Android

1. Click the image you want. 
2. Press and hold the image to save.
3. Press the menu button.
4. Tap the option wallpaper.
5. Choose the option gallery and then press set wallpaper and enjoy.

APPLE

1. Click the image you want. 
2. Click the share icon on your safari browser (box with arrow pointing up).
3. Click save image.
4. Now you can enjoy your fresh new wallpaper in your camera roll.