@joydeb12,
Don't.
The bigger anti-virus companies are reliable. They are McAfee and Norton (Symantec). I've been using computers a helluva lot longer than you have and have never heard of what you're proposing to download on your computer. It is highly likely that it's a spyware scam.
BIG HINT - NEVER, EVER, EVER download something if you don't know what it is or what it does.