Click on the Layers link from the Main MAP Navigation, and wait for the layers to load. Eventually both NRC and the USGS WMS servers will be avialable.
Click on the Tools link from the Main Map Navigation, and wait for the tools to load. Eventually you will have a pallette of tool options including two SOS links.
Click on the second SOS tool (with a small grid on the icon) and a few options for selecting a sensor(s) by bounding box will appear. The options are to either query the NRC server or the current USGS server. USGS is selected by default. There is also a check box that toggles a ZOOM PROTECTION for the Canadian NRC server. If it remains checked then a rather close level of zoom is required before an actual getSensorByBoundingBox is actually performed. You may of course uncheck that box, but be warned that your wait time and possible timeout may occur.
Turn on either an NRC layer or USGS layer (AFTER CLICKING THE LAYERS BUTTON DIRECTLY UNDER THE MAP TO LOAD LAYERS) to reveal the various locations of sensors as a guide or prompt to avoid any hunting and pecking.