Below you will find the best practices to utilize the Freeform shape tool to help with your drawings.
Location:
The tool is located on the Home Tab 
How to Draw a Line:
After you have selected the tool, single left click and release to start the line, extend the line and double click to finish.
How to Draw a Dig/Post:
If you want to create a post or a dig route, single left click and release to start, single left click and release again to create a point, now you are able to extend the line in another direction. When you have the correct angle, double click to finish the line.
How to Draw a Line with a Curve:
Single click and release to create the first point, then extend the line to where you want it to finish, once there double click and mark the end point.
If you right click that line select Edit Points and this will select the line and a black boxes to the two points (or as many as you added to the line). If you left click on of the boxes, it will show a white box which you can click & hold that box, drag it to create the exact curve you desire. Adjust the start and end points and create a curve with multiple angles.
Edit Points Video: