This basically produces a tube. We want the tube to have a shape which has a bulb on one end and tapers off to a point at the other. This will require a few steps.
1) Select the left view camera (click on "front" and select "left").
2) From the Geometry menu, select Extrusion Envelope, then Symmetric.
This will change the dimensions of the cross sections that will be added in both the Z and X directions symmetrically.
3) Click the left end of the sweep path (there will be a light purple line running from left to right which is called the sweep path). Move that to the left edge of the grid. Do the same for the right end of the sweep path. This will make the length of the tube the same length as the grid.