Depending on how you configured Kurviger there are two options to do this, the crosshair mode and the bubble mode. We recommend to enable the crosshair placement (Settings|Map) mode, this makes it a lot easier.
If you want to delete the whole route you can use the clear button (Routing→Clear) or long press the route and select clear.
With crosshair mode, you only have to long press on a waypoint and select Delete.
With the bubble mode, waypoints can be deleted via the waypoint menu (Routing→Waypoints). Select a waypoint and press on the X.