Reference list:

Public Health England (2019). One You Couch to 5k (Version 7.1.0) [Mobile app]. Google Play Store. https://play.google.com/store/apps/details?id=com.phe.couchto5K&hl=en_GB

The citation in your text will be:

(Public Health England, 2019)

If you have used the developer or license holder's name in your sentence then only the year of publication is placed after it in brackets, e.g.

Public Health England (2019) have created an app that helps people increase their fitness from sedentary to being able to run five kilometres…