The first time I used this App (Mid April2017 - pre updates) I had a few error messages on the screen before my first "launch" and it was all a bit nerve-wracking not having control.
The Hangar360 app takes over control of your drone - therefore the DJI Go4 app must be closed (after setup) before the Hangar360 app is opened.
Then follow instructions on the app.
The App will auto take off and go zooming up to 300ft - stop and for 5-6 minutes it will take 27 photos in sequence.
Then it will prompt you to carry on flying or come home. "carry on flying" means take another 360 photo!!!
If you are done it will come vertically back down to its launch site (I don't know how it deals with VRS if its a still day - I has a good breeze blowing and a storm approaching). When safely landed do not turn off the drone or close the App as it needs to upload the photos from the drone to the 360 App.
When that is done, you have the option to upload to Hangar now or later, for processing - I recommend uploading later (on wifi) as it takes a long time uploading and then waiting while Hangar processes the images and sends the finished 360 image back to the APP.
During the Hangar360 flight, the only way to take back control, in an emergency, is to exit the 360 app by switching the controller into SPORT mode and back again. Then you will need to open your DJI app to regain control.
My first 360 photo: Above the Chiltern Hills, UK.
Hangar 360 Photo