how do I change attributes of part of way in JOSM

Using JOSM I have a long road I traced from a GPX track and some if is unpaved how do mark parts of it =unpaved?
using Potlatch I would use “X” to make it a new way then set that ways attribs, how do I do this in JOSM?

Unpaved roads are often called ‘highway=track’, where the road condition can be specified using the ‘tracktype’ tag. Both tags are described on the Map Features page.

Split the way at the points where the surface changes? (In the JOSM menu bar: Tools | Split Way.) Then you can tag the separate parts with different highway= tags.