1. Select an image you like
2. Press Download button above the image
3. By clicking Download button you are automatically redirected to wallpaper cropping tool, where image size is automatically suggested by your desktop size.
You can change this image size by entering size you need in pixels. Then click Change Selection button to preview cropped image borders.
Also You can crop a little peace of original image, to save as wallpaper. To do so, slide the borders of cropping tool, on the image like shown on image below:
4. Then press Generate and save new size image from selection button. The wallpaper will be downloaded automatically.