•
Switch into Cone Surface Creation mode by
pressing the Cone Mode Tool 
or by selecting "Cone Mode" from the
Surfaces sub-menu (ribbon toolbar’s Create Tab).
The cursor will change to the cone surface cursor.
• Select the end point or the base curve of the cone.
The selected object will highlight. Note: The base curve of a cone does not have to be closed using an open curve will create an 'open' cone.
• Select the opposite end of the cone (i.e. if you selected a point first, now select a curve. If you had selected a curve now select a point).
The second object will highlight and the surface will be created. Note: the direction a cone faces is determined by the direction of the curve being used. If the surface you create does not face the direction you would like you can use the "Flip Surface(s)" command, located on the surface sub-menu. This command will flip the currently selected or, if no surfaces are selected, the last created Surface. Surfaces also have a "double sided" property that will mean a surface 'faces' in both directions. See Surface Properties.
Note 1: at any time during surface creation you can abort the surface by selecting "Cancel Surface" from the right-click or surface menus, or by pressing [esc].
Note 2: Object selection behaves differently during surface creation. Multiple objects can be selected without using the shift key to extend your selection. Selection highlights are cleared after each surface is created.