The Legend is rendered by a custom ItemsControl. By default it is placed to the bottom of the chart and aligned to the middle. If you want to change the position and/or the alignment of the legend control, you'll have to overwrite the default char template - check the "General Template" section to see how.
Some of the legend settings are accessible through properties - LegendWidth and LegendHeight let you customize the size of the legend, LegendOrientation lets you choose how the labels are drawn. Together those properties allow you to customize the layout of your legend.
The legend labels are retrieved automatically from the Series.Title property. If the Series is drawn with scatters, a matching symbol is drawn in the legend.
