The Site Settings section in the Studio 8 theme Customizer contains 4 options. Navigate to Appearance → Customize → Theme Options → Site Settings to access these settings.

Options

• Site Width (Text) — Maximum width of your site (PX or % units, default: 1320px).
• Curtain Thickness (Slider) — Thickness of the decorative curtain border around the body (0–100px).
• Curtain Background Color (Color) — Background color of the curtain border.
• Curtain Background Image (Image) — Background image for the curtain border.

After making changes, click Publish at the top of the Customizer to save your settings.