Hi Saraohara
To change all the layout of you website you change from Appearance/theme options/Default Layout Options and to change the layout of the particular page / post you just edit the particular page / post and at the below of the editor there is layout. Its for the particular page. Select to any layout you want.
If you have dont this in correct way then it must work because we dont have other client issue on this layout. If you still facing the problem then just send your username and password details in our forum.