We have detailed instructions in our Online-help Design Manual or by opening Design, going to the ‘pull-down’ menus Help > Online User Manual, entitled “Drawing a Smooth (curved) Polyline” that will assist you with drawing a Smooth Polyline.
Alternatively, you can view the Tutorial Video in Part2A – Drawing tools and Part 6 Smooth (curved) Polyline. To view the Training Video PDF with the links to YouTube, log into the My Account page then go to Downloads>Design Training Videos or use this link.
Here are some other tips for using the Smooth Polyline Tool:
Ensure that your Constraints are turned off
If you are having problems getting the polyline to ‘curve’ in the direction you want then try changing the Start Angle either by entering in a new angle in the modifier text box or using the tangent tool adjacent to the Start Angle text box
Create a straight polyline then use the middle grip to create the curve ensuring constraints is turned off.