Blog page content too narrow

Site URL: https://tuba-caper-7mj2.squarespace.com/blog/2015/10/14/preserved-lemons-br3e6

Hi, 

I need some help resizing the content on my blog page. Currently everything is centred into a very narrow block of text, which you can see here: https://tuba-caper-7mj2.squarespace.com/blog/2015/10/14/preserved-lemons-br3e6

The same thing is also happening on the main blog page: https://tuba-caper-7mj2.squarespace.com/blog

In terms of the main blog page I would like to have the posts stacked with a square image to the left hand side of each post, and then to have the title and excerpt to the right of the image. I've attached a rough image below of what this should look like.

I've tried many solutions from the forums and couldn't get anywhere with this. So any help would be greatly appreciated. 

Thanks in advance, 

Abbas