Bottom margin on sidebar

Hi,

Thanks for the fantastic theme, I have no prior experience in web development and am really enjoying creating a site.

I'm having a small problem with aligning the bottom of my right sidebar with the bottom of my last post, which both have distinct backgrounds. It currently runs all the way into the footer.

I've tried adding padding (moves the text around inside the container) and margins (does nothing) to create the gap but to no avail. Help would be greatly appreciated and please give an example if it involves coding as have been working through the medium of trial and error...

Many thanks,
Pete