Check out example codes for "flutter how to space buttons evenly in a row". It will help you in understanding the concepts better.

Code Example 1

//Use mainAxisAligment: MainAxisAlignment.spaceEvenly,
//After initializing the row

new Container(
          alignment: FractionalOffset.center,
          child: new Row(
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: <Widget>[
              new FlatButton(
                child: new Text('Don\'t have an account?', style: new TextStyle(color: Color(0xFF2E3233))),
              ),
              new FlatButton(
                child: new Text('Register.', style: new TextStyle(color: Color(0xFF84A2AF), fontWeight: FontWeight.bold),),
                onPressed: moveToRegister,
              )
            ],
          ),
        ),

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