Hi

The step is to take the real smooth tools, and there, under the smooth interpolation types it's the second icon that let you chose the edges to be creased.
But beware ! You might want to do it at the very end , because there is a bug that move away the edge selection randomly to some other edges if you continue to add some geometry (ex: extrusion). It's not a big deal, but the work must be (re-)done again.