You can use the Set Decking Direction tool to change the direction of your deck boards.
To change the direction of deck boards:
Select the deck by clicking on one of its edges.
Right-click and select Set Decking Direction, or select Edit > Modify Elements > Set Decking Direction.
Select two points to define a line that runs in the direction you want the deck boards to run. The deck boards update to match the direction of the line.