Log in to Facebook and access the group you want to delete from the Groups button on the home page. It will be in the left-hand navigation pane.
You will need to remove each member individually. Click the edit icon next to each member’s name, click Remove member then Confirm.
When the other group members have been removed, click the edit icon next to your own name and choose Leave Group. Clicking Leave Group will delete the group. Users will not receive a notification that it has been deleted.