Click on that gigantic 'Download Now' icon over there to download VoiceAttack.
Once downloading completes, you will need to run the VoiceAttack installer.
If you are a Windows XP user, chances are that you may be in need of the Microsoft Speech Recognition Engine. Those components are available via the big, 'XP users click me' button over there. Don't worry. VoiceAttack will give you a link back to here if you do not have the required software on your computer.
The trial version of VoiceAttack gives you one profile with twenty commands. It allows you to preview VoiceAttack for 21 days. After that, you will need to purchase a registration key from here