When I upgraded from Awesome Blogger template to Emporio Blogger theme, I discovered that Blogger has removed the option to adjust the width of blog and sidebar from the Blogger theme designer.
Many users who are happy with this have been bombarding the Blogger forum to lament their frustration. Well, Blogger has listened and have now added the option to customize the widths of the sidebar and posts stream of the new Blogger themes via the Blogger Theme Designer.
To customize the widths, sign in to your Blogger blog, navigate to “Theme” > “Customize“ >, click “Advanced,” and there you will find a “Widths” section.
Here is a video demo :
I hope it works for you.
NB: If it doesn’t work for you, that means you are using an old Emporio Blogger theme. Upgrade to the latest version of the Blogger Emporio theme.