README.md in capistrano-systemd-ng-0.1.3 vs README.md in capistrano-systemd-ng-0.1.4

@@ -21,10 +21,16 @@
 
     $ gem install capistrano-systemd-ng
 
 ## Usage
 
-Add these lines to your Capfile:
+Please activate the Capistrano `app`role in `config/deploy/staging.rb`and/or `config/deploy/production.rb`:
+```
+ role :app, %w{[e-mail]}
+```
+Replace `example.com` by the domain name used by your server.
+
+And add these lines to your Capfile:
 
 ```ruby
 require "capistrano/systemd/multiservice"
 install_plugin Capistrano::Systemd::MultiService.new_service("example1")
 install_plugin Capistrano::Systemd::MultiService.new_service("example2")