part of the origional DJI app has a ground station section.
1, Go to settings in app and enable ground station.
2, Turn on Go Pro (doesn't need to be recording)
3, Turn on phantom
4, Make wifi connections
5, Open DJI app and go to where the camera view is swipe to the right/left (i forgot which) to open the map for ground station. Ignore the warnings.
6, Hit the back arrow to go back to the FPV view and it should appear, if not try another app there are a few on the app store (paid) that do work.
also try to forget the phantom wifi connection in your iPhone settings before you start you don't have to do this every time but it may help.
If you have some spare cash get a cheap android phone because all the functions work straight away, also there are better apps for controlling your phantom. Im an apple kind of guy but i use an android device for controlling my phantom.