RAW for Canon Powershot A540?

I have successfully installed CHDK on a SD card inserted in my Powershot A540. I would like to know how do I shoot RAW pictures? What are the setting in the <Alt> menu of the camera that should be done? What are the in-camera settings to shoot RAW photos using Canon Powershot A540 digital compact camera? What are the RAW parameters that should be set in the CHDK in-camera menu? If someone can advise, it would be wonderful. Thank you.

I shot some pics with the file name as: CRW_xxxx.CRW & IMG_xxxx.CRW. But these files do not open up in Adobe Photoshop Creative Suite 5 (CS5) extended edition. Which image editing / RAW processing software should be used? Any links?