The top part is the ADF indicator. The yellow needle is pointing towards the selected waypoint relative to the longitudinal axis of the aircraft. The compass card can be manually rotated using touch and swipe up/down gesture on the left or the right of the indicator. This way you can set the ADF to the magnetic heading. Below the main indicator the name of the active waypoint is displayed as well as the distance from the waypoint (great circle distance) and GPS accuracy. It is possible to select any kind of waypoint (Airports, VOR, NDB, etc) as an ADF target waypoint unlike with a real ADF which requires NDB or AM transmitters as waypoints. You can select a new waypoint from the database with the the blue disclosure button on the bottom part of the instrument. Please read «Selecting waypoints from the database» to get information about waypoint search and selection.