I'm a complete newcomer to smartphones and have not much idea how they function. I've bought a Redmi3 which works fine for phoning. I have successfully installed and am using Whatsapp and Evernote but when I tried to install ryanair's app (just to be able to register online and use the boarding card from the phone) I get an error message from Google Play Store "You don't have any devices". I can 'wander' around the google play store but can't see how to join my R3 to this part of the google system. I have my gmail account working ok on this phone and can open my account on google ok. So clearly, google knows that I have a Xiaomi Redmi3 device. I have tried downloading and installing google play store app as an alternative to the system's app store. It install fine but it doesn't work. Reading all the stuff on this forum, it seems likely to me that the Xiaomi system stuff prevents me from using 'unwanted' third party apps. Is this correct ? What is the solution ? Do I have to get the phone 'unlocked' - whatever that means ? Apart from this problem, I don't have much to complain about on the phone. Thanks in advance for any advice and explanations.