In XAML, this code will allow you to add a control to a specific row/grid in a XAML Grid.
Button butHelloWorld = new Button();
butHelloWorld .Content = "HELLO!";
//add other attributes including onclick properties
int row = 1;
int column = 5;
Grid.SetRow(butHelloWorld , row);
Grid.SetColumn(butHelloWorld , column);
gridMyGrid.Children.Add(butHelloWorld );