Form_for for a has_one relation model

Hello guys, I’m new in rails and I have the following question:

I have two model

user and user_informacion:

class User < ActiveRecord::Base
attr_accessible :email, :password, :password_confirmation
has_one :user_information
has_secure_password

before_save { |user| user.email = email.downcase }
before_save :create_remember_token

VALID_EMAIL_REGEX = /\A[\w+-.]+@[a-z\d-.]+.[a-z]+\z/i
validates :email, presence: true, format: { with: VALID_EMAIL_REGEX },
uniqueness: { case_sensitive: false }
validates :password, presence: true, length: { minimum: 6 },
confirmation: true, unless: Proc.new { |a| !a.new_record? &&
a.password.present? }

def send_password_reset
self.password_reset_token = SecureRandom.urlsafe_base64
self.password_reset_at = Time.zone.now
self.password = self.password
self.save!(:validate => false )
UserMailer.password_reset(self).deliver
end
def reset_password_token
self.password_reset_token = nil
self.password_reset_at = nil
save!
end

private

def create_remember_token
if self.new_record?
self.remember_token = SecureRandom.urlsafe_base64
end
end

end

class UserInformation < ActiveRecord::Base
belongs_to :user
attr_accessible :address, :address2, :business, :descripcion,
:identification_number, :mobile_cell, :name, :phone_number
validates :address, presence: true, length: { :maximum => 250 }
validates :address2, length: { :maximum => 250 }
validates :descripcion, presence: true, length: { :maximum => 300 }
validates :identification_number, presence: true
validates :phone_number, presence: true, length: { :is => 11 }
validates :mobile_cell, :length => { :is => 11 }
validates :user_id, presence: true
end

As you can see User has_one UserInformation

My routes are like this:

resources :users do
member do
resource :user_information
end
end
resources :sessions, only: [:new, :create, :destroy]
resources :password_resets

root to: ‘users#new’

match ‘/signup’, to: ‘users#new’
match ‘/signin’, to: ‘sessions#new’
match ‘/signout’, to: ‘sessions#destroy’, via: :delete

I having a lot of problem tying to figure out how to make a form_for for
my
create action of my user_information. I tried with
form_form(@user_information) do |f|, form_for([user,
user.user_information.build]) do |f| but I always get an error. Does
anyone
can help me with this form_fom, please??? The form_for if for my new
view
of may user_information.