The NAV Beacon icon shown in your HUD is usually not the actual beacon but a representation of where the NAV Beacon can be found (wall-o-text):
The actual NAV Beacon itself will usually display as a WHITE icon in your Sensors display, almost straight ahead of your ship, usually near center but often slightly off to one side or the other and often a little bit high or low. Pointing the ship at it and designating it as a target (I use the "Target Ahead" button) will start a scan of the beacon which will take several seconds to complete. As the scan progresses, in the TARGETING Panel left of the HUD where it says NAV BEACON you will also see a spinning "wait" icon and hear a "scanning" sound-effect. When the scan completes the "wait" icon will stop spinning and you will hear a different "scan completed" sound-effect. You can now open the NAVIGATION tab in Panel #1 to see all of the system's planets, belts, current USS, etc. listed there.
It should be noted the NAV Beacon must remain in FRONT of your ship as the scan proceeds so you should SLOW DOWN or even STOP while your ship completes the scan. It should also be noted that other nearby ships will scan YOUR ship as you are scanning the NAV Beacon. If those other ships are Pirates and you have Cargo, you might be attacked for your cargo.
The way I do it: Drop in on the NAV Beacon and STOP. Point the ship at the white, NAV Beacon icon in the Sensors display (usually almost straight ahead, about 2 Km), designate the white NAV Beacon icon as a target using the "Target Ahead" button and then drive slowly toward the icon as the scan progresses. When the scan completes go full-throttle, BOOST past the NAV Beacon (don't run into it) and try to re-enter Supercruise. You will be mass-locked and the SC indicator will usually fill up slowly but, keep BOOSTing and you will eventually re-enter SC. Immediately on entering SC you can throttle down to zero (32 Km/sec) and examine Panel #1>NAVIGATION tab. o7