Page-specific left and right sidebars with Twenty Eleven 1.3 child theme?

Hello, I’ve made a Twenty Eleven child theme for a new version of my website (not currently online).

I want certain pages to show the sidebar on the left, just to keep things interesting really.

How can I do this?

Thanks!

Edit – I should probably mention, my CSS and HTML knowledge is ok but for anything to do with PHP I’ll probably need pretty specific instructions.