Example on how you can upload customers to desk.com using the desk_api gem.

upload.rb

require 'desk_api'
require 'csv'

DeskApi.configure do |config|
  config.username = 'you@example.com'
  config.password = 'Top$ecret1'
  config.endpoint = 'https://example.desk.com'
end

CSV.foreach('./customers.csv', headers: true) do |csv|
  DeskApi.customers.create({
    first_name: csv['first_name'],
    last_name: csv['last_name'],
    emails: [{ type: 'home', value: csv['email'] }],
    phone_numbers: [{ type: 'home', value: csv['phone'] }],
    custom_fields: {
      id: csv['id']
    }
  })
end