How to open .CHM file using RoboHelp

Hi All,

I am having a .CHM file generated with other than RoboHelp. I want to edit this .CHM file. But RoboHelp is not allowing me to open this file. RoboHelp is generating .CHM file with .XPJ input. What is the process of opening a .CHM file using RoboHelp? If any one knows about this let me know.

Thanks in Advance,
Sarat Chandra