content width

You can use the following CSS to increase the width of the post content container:

.entry-container {
  padding: 0 5% !important;
}

If you haven’t seen it already, you should also check out the Tracks CSS Snippets collection: https://www.competethemes.com/help/tracks-css-snippets/

It’s full of similar CSS snippets you can copy & paste to customize your site.