Reply To: Changing the Width of the Sidebar

Hello

Add this in Appearance > Customize > Additional CSS

@media screen and (min-width: 768px){
    #primary{
        width: 66%;
    }
    #secondary{
        width: 31%;
    }
}

change 66% and 31% to the widths you need.

you will notice that 66 + 31 = 97. This allows a 3% spacing between the main content and the sidebar.