Please let me share with you my full guide, from setting up your new Nano2 to developing apps for your android smartphone: "Arduino IDE + Android Studio for RedBear Nano 2.0"
I encountered several confusion while starting out with my RedBear BLE Nano Kit v2.0 so after my research I am finally ready to develop my prototype project. Many of us would like to develop Android apps that could transfer data to and from the Nano2. This is what this guide is all about: creating a firmware for Nano2 and its relevant native Android app.
I use Arduino IDE with the example code of BLE_HRM, Board: "BLE_Nano2", Programmer: "RBL_DAPLink" (find under tools). Also, I use nRF Toolbox master app cloned from github to my Android Studio as a basis to develop a relevant app. Running each example on the Nano2 and my Samsung J5 '16 accordingly, I can use the HRM app from the toolbox, make edits on the code, recompile and see the results.
For any beginners this may be useful since are many unanswered beginner topics laying around. Thank you and enjoy love your nanobear as much as I do!