In order to install a background, please do the following:

1) Unzip the downloaded ZIP file
2) Move the BMP file towards the directory of your choice
3) Go to the properties of your screen (right mouse click on your current wallpaper and choose properties)
4) Select the TAB "Background"
5) Click on the "Browse" button and go towards the directory used in step 2
6) Select the BMP file
7) Click on the "Apply" or "OK" button to save
8) If everything seems to be all right then click on the OK button