Help with page layout please

I have a WP site up for a client – https://www.upwardaction.com/test

For the inside page layout, I do NOT want the three columns to show up – just the tag at the top, the banner under it (not currently visible – the tabs for navigation,and then to sidebar and content area.

The three columns should only show on the Main Index Page.

The html for the three columns is in the header.php file. When I move it to the Main Index Page file, it gets rid of the sidebar and wonks up the layout. When it’s in the header, it’s fine.

I know this is something small (unclosded div or some such) but I cannot find it. Help ??