Start with a rectangle.￼
Choose the fillet tool, choose the 3rd mode on the mode bar, then click on the last button on the mode bar. This button is the preferences or settings button and it is where you enter the fillet radius for this tool and it sets the fillet radius for then next two techniques that I want to show you.
If you have Click-Click drawing set as a VectorWorks preference, click on the first line then click on the second line. This places a fillet at the corner.
A quicker way to do this is to use the 2D Reshape Tool. This tool has a mode for changing the vertex type (the second mode on the mode bar). This means that wit one click you can change the vertex type from corner point (pointy corner) to a fillet corner (chose the fillet corner button on the mode bar).
And I know one more way to do this quickly. Make sure the rectangle is selected. We have a command on the menu bar:
Modify > Poly Smoothing > Arc Smoothing.
This will fillet all the corners at the same time, but the object has to be a polygon...