This article will show you how to edit the Mega Menu Wrapper on your site.
Instructions
Navigate to Modules and on the Site Tools tab, and then select Design Center:

Select the Theme Manager:

Select the appropriate Layout and Theme:

Click on the Fifth Style:

Verify the Main Navigation drop-down menu says Mega Menu Wrapper:

Make modifications to the Background & Border tab:

Background Color: Modify the color of the background
Background Gradient: Edit the background gradient
Note:
Background Gradients are supported by modern browsers, but in Internet Explorer 9 or below, they will display as a solid color that is an average of your start and stop colors.
Background Image: Upload a background image
Border: Set the style, width, and color of the border
Choose a saving option at the top:
If saving these changes to only the current theme, click Save Changes:

If saving and pushing these changes to other themes, click the drop-down next to the Save Changes button and select Save and Push Changes to Other Themes:

Choose the themes you want to push to

Select Save and Push Changes
