To add a badge design to a credential group just following these steps:
1) Log into your Accredible account
2) Select 'Groups' from the top menu
3) Select the group you want to add the badge for
4) Select the "Group Settings" tab
6) Click 'Credential Appearance' in the left hand menu
7) Hit the 'Upload Badge Image' button.
7) Hit save and you're done!