No, it doesn't cost anything extra beyond what you're paying for the unlimited data plan. As far as hooking it up, go to settings/Wireless & Networks/Mobile Hotspot Settings and that will take you to your settings. Your SSID will already be listed. You will have your choice of security settings. Pick a password and put that in the Password area to replace the default password. Then you just need to go to your computer's wireless settings and set up a new connection using the information in your hotspot settings. After that, when you turn on your hotspot and your computer, your computer should either automatically connect, or give you a choice of available connections, depending on how you set it up. After that, your connection will depend on how strong of a 4G area you're in.
Also, you can go to the Verizon website and get the hotspot instructions and download the users manual.
HTC Rezound Support
Hope that helps
Edit: Just to make sure you know, you can turn on your hotspot from the settings menu, from the pulldown status bar info under Quick Settings, and there is also a hotspot widget you can put on a home screen.