Please check this example code. It may be useful :example code
you just need to add legendGroup and its property position as mentioned below.
var legendPosition = new sap.viz.ui5.types.Legend({layout: {
position: "left"
}});
var column = new sap.viz.ui5.StackedColumn("chartStackedColumn", {
width : "80%",
height : "400px",
title : { },
dataset : dataset,
legendGroup: legendPosition
});