[Theme Horse Support Team]

Hi,

Go Appearance > Customize > Additional CSS and paste below CSS code to reduce the width of the content:

@media (min-width: 992px) {
    .single .col-lg-8.content-area {
       -ms-flex: 0 0 66.666667%;
       flex: 0 0 66.666667%;
       max-width: 66.666667%;
    }
}

Note: Please reduce the above all 66.666667 digit value to your desired width.