If you don't have any WebTV hardware, you can also use software on your PC.

The WebTV Viewer isn't as accurate or feature complete as an actual box, but it'll give you the general experience

Emulating WebTV for Dreamcast via Flycast will give you a slightly more accurate experience, but is more difficult to set up and use.

WebTV Viewer
Less Accurate - Easiest

Flycast
More Accurate - Hardest