set secret keys for amazon aws3

I use fog and carrierwave. Right now I just have simple uploader that I run locally:

CarrierWave.configure do |config|
    config.fog_credentials = {
        :provider               => 'AWS',
        :aws_access_key_id      => ENV['S3_ACCESS_KEY'],
        :aws_secret_access_key  =>  ENV['S3_SECRET_KEY'],
      :region                 => 'us-west-1', # Change this for 

  }
  config.fog_directory  = "bucket-main"    
end

But now I have a question where should I save my secret keys.

On heroku environment I could print like this

$ heroku config:set S3_ACCESS_KEY=THERANDOMKEYYOUGOT  
$ heroku config:set S3_SECRET_KEY=an0tHeRstRing0frAnDomjUnK  
$ heroku config:set S3_REGION=us-west-2  
$ heroku config:set S3_BUCKET=my-sample-app-bucket-20160126

But I don't know what to do on my local machine.

I've followed this tutorial http://ift.tt/1Kvk5J8

And stored my keys in config/secrets.yml file which I just created:

development: &defaults
  S3_ACCESS_KEY: "AKHJJHHJHJJHHJHJDHJDDJDHJDHJDJHDRANDOMFQ"
  S3_SECRET_KEY: "HfkdjgjkfjkgjkfjkRANDOM2JSJDKKJJKSSJDJKSKaN"

test:
  <<: *defaults

# Do not keep production secrets in the repository,
# instead read values from the environment.
production:
  <<: *defaults

But rails s command gives me this error: /home/jonstark/.rvm/gems/ruby-2.3.0@railstutorial_rails_4_0/gems/fog-core-1.35.0/lib/fog/core/service.rb:244:in `validate_options': Missing required arguments: aws_access_key_id, aws_secret_access_key (ArgumentError)

Soo what do I do?