Toolbar: 
Geometry toolbar 


Menu: 
Add menu > Geometry submenu> > Add Spline 

What to do: 
Note: Add Spline is the only sketchelement [other than Add Point] in which you do NOT drag your mousepointer.
The Spline sketchelement is now in the graphicarea. 

An open and closed Spline. 
Notes:
To show the splinehandles, click the Spline.
To hide the splinehandles [default], click the Spline again. 

To edit its geometric properties: 

Edit the Node's Position Use the PartEditor:
Use the Point Display and Properties dialogbox
Edit the Spline's Angle at the Node
Edit the Spline's Curvature at the Node
