Are you using the Active Admin gem? Active Admin bundles in Devise for
managing adminstrative users (which could be completely separate from
whatever your application does with user registration and
authorization).
Do you need to know how to get into it for the first time, so you can
set up users?
Do you have a current installation using Active Admin with Devise that
you cannot get into because you don't have credentials?
If you do have credentials to the application data base, you could
hack the users table, but I don't really recommend doing that.