All you have to do is go to the play store on your Android, dowload the app "Electroneum". Then just sign up verify your number and then you can start mining straight away by clicking "start mining" on the home page. To earn more coins press the "More" button at the bottom right of the screen, then click "referral program" and type in BE299B or scan the bar-code above.
Hopefully this helps, if you have any other questions feel free to ask :)