Many of these camera devices have RTSP support that can be used in Video Players that have network playback capability. However, try to log into the Administration area of the camera to see if you can use the URL (usually formed from the IP) of the camera.
Also, many manufacturers have an app that comes as an addition to the devices so yo can use it to watch the stream.
Additionally, you can use the IP of the camera (if it's public!) to watch the stream in the browser while using the Preview mode.