Adding New Admins to Active Admin

What Brian said works, but if you want to set the password in the interface rather than have it send a reset email try this:

Leave the admin_user model at its original generated default, then in app/admin/admin_users.rb:

ActiveAdmin.register AdminUser do
  index do
    column :email
    column :current_sign_in_at
    column :last_sign_in_at
    column :sign_in_count
    default_actions
  end

  form do |f|
    f.inputs "Admin Details" do
      f.input :email
      f.input :password
      f.input :password_confirmation
    end
    f.buttons
  end
end

What brian said works perfectly http://net.tutsplus.com/tutorials/ruby/create-beautiful-administration-interfaces-with-active-admin/

AdminUser.create!(:email => '[email protected]', :password => 'password', :password_confirmation => 'password')