well, it depends. You want to set this from the designer or programmatically? When you don’t know how to do something through programming, doing it through the designer and observing the changes made in the code by the Designer is not a bad idea.
Also, is this setting for a single row or for the whole column? The code (in C#) will be different, of course, depending on what you want to do.
If you are defining a column, you can simply use column1.HorizontalAlignment = Xceed.Grid.HorizontalAlignment.Right;
If the setting a for a single row, it would rather be: