I just want one sidebar

I've installed BeTheme and now I don't want the full width lay-out for my blog, but I'd like to have the sidebar lay-out. I clicked the 'right sidebar' for my blog and it works fine. But the only problem is: I have to choose two sidebars which are split up in columns. I would like to have just one sidebar, and that's possible, only the one sidebar doesn't spread over the whole sidebar area. So it sorts of 'crops' everything to one column and leaves the second column blank. Is it possible my one sidebar fills it all up? I already tried to put the same sidebar in both sidebar options. Didn't work well.