Imbalance theme, add sidebar to homepage

I want to add a sidebar to the homepage of the imbalance theme, as has been done on topwpp.com. As standard, the sidebar only appears on post pages. I have managed to remove the third image column on the home page (by making an edit to the Java file columnize.js, changing 3 columns to 2), so ‘all’ I need to do is call the sidebar, set the width and float it to the right using code something like this (<div id=”sidebar” style=”float: right; width: 335px;”>
</div>), but I have no idea where to add this code. To the index.php? If so, where? Or is it more complicated than this? Do I need to ‘register’ the sidebar somewhere?

You can find all the theme files here: https://github.com/wpshower/imbalance

Thanks in advance for any help.

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