You can edit your global groups from within the Design Manager.
- Navigate to Content > Design Manager.
- Click Global Groups in the left-hand menu.
- Find the Global Group you'd like to edit and click the name to see the layout.
- Click the gear icon on any of the modules in the group and select Edit Options or Edit CSS to make content or styling changes.
- Once you've made your changes, click Done in the Options or CSS dialog box, then click Publish Changes.
Your changes will apply wherever this Global Group appears.