Вы хотите реализовать ItemizedOverlay в классе MapActivity.см. пример.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.drawable.navup);
MapView mapView = (MapView) findViewById(R.id.mapview);
mapView.setBuiltInZoomControls(true);
// Get your GeoPoints from SQLLite and use them below for Longitude and Latitude
GeoPoint point1 = new GeoPoint(latitude,longitude);
OverlayItem overlayitem1 = new OverlayItem(point1, "City", "State");
List<Overlay> mapOverlays1 = mapView.getOverlays();
Drawable drawable1 = this.getResources().getDrawable(R.drawable.map_pin);
ClevelItemizedOverlay itemizedoverlay1 = new ClevelItemizedOverlay(drawable1, this);