Try opening the RoboHelp HTML application (not the RoboHelp for Word application used to create the .HLP file). There create a new project specifying to import the HLP file. From memory that does a pretty good job of bringing across the content. Once there it is easy to create a CHM file. If you need to know more specifics, you'll need to tell us which version of RoboHelp you have.
I understand that Catherine but what you require is a lot of hand holding, training and advice. This is a user to user forum and as such we too have demanding jobs. I can help, but it will have to wait until I am able to help. If you can't wait, try reading the product help files. They are relatively good for fairly basic queries like this. If you require further help, contact me using the email link in my profile. Alternatively there are some books around that could help. IconLogic have one that has been updated for RoboHelp 10 and can be found here: http://www.iconlogic.com/robohelp-html-10-workbook-adobe-iconlogic.htm
we are trying to generate .chm because we are migrating the application to 64 bit from 32 bit and those help files must also be changed from .hlp files.we want to know how to link the generated .chm files with that application?..