Each environment is different, but the basics are the same. Chances are you might already have everything you need to run Web Captioner.
Microphone or other audio input device
You'll get the best result when the person that is speaking is wearing or holding a microphone. You could use basic earbuds with an inline microphone, a lavalier microphone, a Bluetooth headset, or even a high-end studio microphone.
Computer running Google Chrome and Web Captioner
As long as it can run the Google Chrome web browser and you can connect a microphone to it, it'll work. This includes Macs, PCs, and Chromebooks.
Optional: A larger display or projector
You could connect your computer to a larger display for your audience to view captions. Or if you're only showing captions to one person, you might just want to have them watch the display on the computer running Web Captioner.