Just remove any blocks from one of the side regions and the main content will fill the space to look like that
Alternatively you will need to edit the theme config.php to set the layout types to only have one of the side-post or side-pre regions
Just remove any blocks from one of the side regions and the main content will fill the space to look like that
Alternatively you will need to edit the theme config.php to set the layout types to only have one of the side-post or side-pre regions