You can adjust how many columns are displayed in the grid layout, and for the related posts in the single post template.

Once you have added the CSS to your site, you will see a Global Styles section at the top (values in the image below may look different depending on which blog kit you are using)

To adjust how many columns are displayed for posts, increase or decrease the px value of the --ds-post-width property.

To adjust how much spacing there is between posts, increase or decrease the px value of the --ds-post-gap property.

To adjust how many columns are displayed for related posts in the single post template, increase or decrease the px value of the --ds-related-width property.

To adjust how much spacing there is between related posts in the single post template, increase or decrease the px value of the --ds-related-gap property.