A basic rectangular shape like those used to represent a process step in a flowchart can have straight or rounded corners. By default, SmartDraw add process steps with rounded corners, but you can easily switch it to a straight corner using the right-click menu.
Select the shape you want to change the corner styling on and right-click to bring up the Corner Style menu.
Choose a square style or the default rounded style.
You can also set a custom radius by clicking Set Roundness.
If you want the setting to apply to all process shapes in your diagram, check to Apply to All box.