Add edrone gem to your Gemfile
gem 'spree_edrone', '~> 1.0', '>= 1.0.1'
gem install spree_edrone
bundle exec rails g spree_edrone:install
At the end restart rails
Login to your admin panel
Go to Configuration -> Edrone Module
Click on "Integrate with edrone"
Provide app_id and app_secret and then click save
app_id and app_secret can be found in the integration section of edrone settings.