To install, extract files to your "World of Warcraft\Interface\AddOns" foler.

Usage:
/rh or /rangehelp

1) Make sure you have the following spells in any of your action bar: 
a spell that works in melee (eg wing clip)
a spell that works in range (eg auto shot)

2) Execute /rh

3) Fill in all fields or use the default spell fill button

4) Confirm settings

5) Enjoy! :)

To customise the range info frame either click the "Customise UI" button in the Range Help setup frame or type '/rh ui' from console.