Setting the Admin in Administrate Gem Rails

I have followed the guide on how to install the Administrate gem in Rails for my app but what i want to add is the ability to set the Admins only by me. I have followed the Gtihub instructions but i am stuk on how to set my email or any other users email to be an admin. Here's what i have added so far:

controller/admin/application_controller.rb

# All Administrate controllers inherit from this `Admin::ApplicationController`,
# making it the ideal place to put authentication logic or other
# before_filters.
#
# If you want to add pagination or other controller-level concerns,
# you're free to overwrite the RESTful controller actions.
class Admin::ApplicationController < Administrate::ApplicationController

  before_action :authenticate_user!
  before_action :authenticate_admin

  def authenticate_admin
    redirect_to '/', alert: 'Not authorized.' unless current_user && access_whitelist
  end

  private
    def access_whitelist
      current_user.try(:admin?) || current_user.try(:door_super?)
    end

  # Override this value to specify the number of elements to display at a time
  # on index pages. Defaults to 20.
  # def records_per_page
  #   params[:per_page] || 20
  # end
end

dashboards/user_dashboard.rb

require "administrate/base_dashboard"

class UserDashboard < Administrate::BaseDashboard
  # ATTRIBUTE_TYPES
  # a hash that describes the type of each of the model's fields.
  #
  # Each different type represents an Administrate::Field object,
  # which determines how the attribute is displayed
  # on pages throughout the dashboard.
  ATTRIBUTE_TYPES = {
    posts: Field::HasMany,
    reviews: Field::HasMany,
    id: Field::Number,
    email: Field::String,
    encrypted_password: Field::String,
    reset_password_token: Field::String,
    reset_password_sent_at: Field::DateTime,
    remember_created_at: Field::DateTime,
    sign_in_count: Field::Number,
    current_sign_in_at: Field::DateTime,
    last_sign_in_at: Field::DateTime,
    current_sign_in_ip: Field::String,
    last_sign_in_ip: Field::String,
    created_at: Field::DateTime,
    updated_at: Field::DateTime,
    name: Field::String,
    password: PasswordField,
    password_confirmation: PasswordField

  }

  # COLLECTION_ATTRIBUTES
  # an array of attributes that will be displayed on the model's index page.
  #
  # By default, it's limited to four items to reduce clutter on index pages.
  # Feel free to add, remove, or rearrange items.
  COLLECTION_ATTRIBUTES = [
    :posts,
    :reviews,
    :id,
    :email,
  ]

  # SHOW_PAGE_ATTRIBUTES
  # an array of attributes that will be displayed on the model's show page.
  SHOW_PAGE_ATTRIBUTES = ATTRIBUTE_TYPES.keys

  # FORM_ATTRIBUTES
  # an array of attributes that will be displayed
  # on the model's form (`new` and `edit`) pages.
  FORM_ATTRIBUTES = [
    :posts,
    :reviews,
    :email,
    :password,
    :password_confirmation,
    # :encrypted_password,
    # :reset_password_token,
    # :reset_password_sent_at,
    # :remember_created_at,
    # :sign_in_count,
    # :current_sign_in_at,
    # :last_sign_in_at,
    :current_sign_in_ip,
    :last_sign_in_ip,
    :name,
  ]

  # Overwrite this method to customize how users are displayed
  # across all pages of the admin dashboard.
  #
  # def display_resource(user)
  #   "User ##{user.id}"
  # end
end