The Eagle Fishfinders use sonar to locate the fish. A transducer takes an electrical impulse and converts it into a sound wave, which it beams into the water. When the sound wave hits an object--which can be the bottom, a structure or a school of fish--the sound wave bounces back to the transducer which converts it back into an electrical signal. This returned signal, or echo, is displayed on a screen. A chart determines the distance the sound traveled.
Press and release the power key. It's labeled "PWR."
Set off for your proposed fishing area. The device will display the depth and water temperature in the corner of the screen. The sonar chart will scroll and will be displaying what's directly beneath the vessel as you move.
Change the display by pressing "ZIN" to zoom in and view more detail. Press "ZOUT" to go back.
Press "MENU | ENT" to bring up the sensitivity menu and use the up and down arrows to adjust the sensitivity. If the screen gets to busy reduce the sensitivity. Eagle recommends what they call a peppered background where scattered dots appear, but individual objects like bottom structures can also been identified. Look out for fish arches, which look, not surprisingly, like arches. You'll see surface clutter at the top and then the arches down the screen a bit followed by the bottom signal. The depth scale is on the right of the screen.
Stop the boat and start fishing. You won't see the arches anymore because the tell-tale arch signal is created by your movement--it doesn't mean the fish have suddenly swum away. The fish will show as a straight line when you are stopped.