Efficiency suggestion for the Mesocolumn

Hello, Richie! I like your theme very much and I would like to do it better. I think the width of text page is very wide on desktop screen – it is not useful and difficult for reading for our visitors. So, they they feel uncomfortable and leave a site quicklier.
Probably, it would be better to add left sidebar to do text content more narrow.
I would be thank for your advice how to add left sidebar easy and elegantly by ready-made solution

(my site)