The instructions at the start list the things you will need. In my case, passport, NI number and passport picture, it even specifies the maximum file size for the picture, I used the picture I used for my last passport application and checked the file size at the same time. I did the application on my laptop and used by Android phone camera and NFC to load the passport details. Once you have your ducks in a row and follow the instructions, it is not too hard to follow the instructions and I gained the Govt ID check app on my phone in the process.