Plug your USB mic in and wait a few seconds for your OS to recognize it. On Windows, go to Settings > Sound > Input and select the USB mic by name from the dropdown. On Mac, go to System Settings > Sound > Input and choose it. Then open an online mic test and make sure the browser is also using the correct device — most test tools have a device dropdown. Speak at normal volume and check that the level meter moves. If the USB mic doesn't appear, try a different USB port (avoid hubs and front-panel ports for initial testing), try a different cable if the mic uses USB-C, and check Device Manager (Windows) for driver issues. Some USB mics have a hardware mute button or gain knob — make sure mute is off and gain is at least 50%. USB mics don't need separate audio drivers on modern Windows and macOS.