You'll want to go to the "Aux" page group, then go to the "System" tab.  

From there you will see a "Status" button on the lower left side of the display.  It defaults to "Status - Software".  

You'll want to cycle that key until it shows "Status - GPS".  

This is also where you can find your datalink status (by cycling the status button one more time).  I've attached a video shot from our bench setup.  Ignore the errors on my unit, as we didn't have GPS among other things connected at the time.