I have downloaded axel-kapt and also installed it through Ubuntu Software Center. But now I don't know how to use axel-kapt, so please tell me how to use it with proper steps.
Axel-kapt is just a GUI for Axel downloader, and provides some settings for Axel. It seems to me that you want to download with Axel, and for that you should use it with FlashGot addon in Firefox. There you can set Axel as default downloader or to use it just for capturing media.