If you still need to chain your geometry into a curve, click the Curve chaining button and chain the curve. See Overview of Chaining for more information.
Click the Pick curve 
button. The dialog box warps into a small button. Click the geometry or curve in the graphics window. The curve must be in the XY plane of the current setup. The Z value of the upper curve is used as the default value for the top of the feature.
When you have selected the curve click Next.
