Only an administrator/moderator can delete a post. But if you catch the error very quickly, like within 30 minutes or so from the initial posting – and if no one has responded to it – you can still EDIT it by changing or deleting the initial contents and leave it blank.

In case you really want to delete the whole thread, you may contact one of the most active moderators, ex:
Charjo or
Don D

or in case of an extreme emergency only, Brian the Keymaster himself, at brian@activemelody.com