Add a way to open the setting page to README.md.

Author: ishikawa999

README.md

@@ -3,10 +3,16 @@
 This is a plugin for Redmine.  
 This plugin changes the translation of the wording on the screen defined in "config/locales/*.yml" in the admin view.
 
-* Normal mode
+## Usage
+
+* 1: Open setting page
+Administration > Message customize
+<kbd><img src="https://github.com/ishikawa999/redmine_message_customize/blob/images/administration_menu.png" /></kbd>
+
+* 2-1: Normal mode tab
 <kbd><img src="https://github.com/ishikawa999/redmine_message_customize/blob/images/normal_mode.png" /></kbd>
 
-* YAML mode
+* 2-2: YAML mode tab
 <kbd><img src="https://github.com/ishikawa999/redmine_message_customize/blob/images/yaml_mode.png" /></kbd>
 
 ## Install
@@ -22,4 +28,4 @@ $ # redmine restart
 ```
 $ cd /your/path/redmine
 $ bundle exec rake test TEST=plugins/redmine_message_customize/test RAILS_ENV=test
-```
+```