// u klasu
private int MY_PERM=1;

//u onCreate

 //ask for permission
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.SEND_SMS)
                != PackageManager.PERMISSION_GRANTED)
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.SEND_SMS}, MY_PERM);