Forerunner 965 accelerometer and gyroscope access

Hi all,

I am working on creating an app for gait recognition for my research, I am trying to access accelerometer data and gyroscope data and store them into a fit file to analyse. However, I am not able to access those two sensors and I am a bit confused about what to do, I tried with something like this:

        var info = Sensor.Info;
        var keys = [];
        if (info has :accel) { keys.add("accelerometer"); }
        if (info has :gyroscope) { keys.add("gyroscope"); }
        if (info has :mag) { keys.add("magnetometer"); }
        if (info has :temperature) { keys.add("temperature"); }
        System.println("Available sensor types: " + keys.toString());

I try to print the sensors availble, as you can see, the result consists [acceletometer, magnetometer and temperrature]. 
I am generally confused about how to access those sensors and if they are activated, plus, does it has anything to do with the watch itself? I am using an Garmin Forerunner965 and I can't find any method to activate developers mode inside the watch. 

Thank you very much for your time and patience!