How to register the mobile no. for login in the Mobikul App?

The mobile app user can register his/her mobile no. for Login in just simple steps.
1. First, the user needs to Login the app account via username (email or social accounts) and password as usual.
2. Then he/she needs to register the mobile no. in the default address.
3. Now the mobile no. is registered & the user can use the mobile no. & the same password for Login the mobile app.