Swim Lanes are the sections dividing the visual so you can categorize processes in your flowchart based on criteria such as whose responsibility they are.
Swim Lanes are on a different Layer from the flowchart so that the lines don't interfere with each other. To work with the Swim Lanes, click the "Swim Lanes" layer tab at the bottom of the screen.

You can add more Swim Lanes to your visual by clicking Add Swim Lane in SmartPanel. A new Swim Lane is added to the last one you select; if none are selected, it's added to the bottom.

You can also remove a Swim Lane by selecting the Swim Lane and clicking Remove Swim Lane in SmartPanel.
You can add titles to each of the smaller cells of the Swim Lanes by clicking in the cell, deleting the placeholder text and typing.