Locate the Style options.
Select from the main menu bar in the Visualization module. The Style options appear at the bottom of the dialog box.
Drag the Line thickness slider to make the streamlines thinner or thicker.
Toggle on Uniform thickness across streams to display all streamlines in the current viewport with a uniform thickness.
Toggle on Show direction arrow to display directional arrows along the streamlines.
Drag the Approx. number of arrows on each streamline slider to increase or decrease the number of directional arrows displayed on each streamline.
Click OK to implement your changes and to close the Stream Plot Options dialog box.