How to use rangefinder on scope?

How do you use the rangefinder on the TASCO R&G illuminated 6-24x50 AOE rifle gun scope? Here's the link for the picture of the crosshairs. http://www.auctiva.com/hostedimages/showimage.aspx?gid=717222&image=331370102&images=331370085,331370089,331370097,331370102&formats=0,0,0,0&format=0