updated README

README.md

@@ -1,24 +1,37 @@
 # Sf
 
-TODO: Write a gem description
+It's a gem to access the Internet2 Salesforce instance with custom objects.
 
 ## Installation
 
-Add this line to your application's Gemfile:
+Add the sf gem to your application's Gemfile:
 
-    gem 'sf'
+For example,
+
+```
+gem 'sf', :git => 'git+ssh://github.internet2.edu/Internet2-TSG/sf.git', :tag => 'v0.1.34'
+```
 
 And then execute:
 
     $ bundle
 
-Or install it yourself as:
+## Usage
 
-    $ gem install sf
+In the hosting application, a configuration file, for example
+`config/restforce.yml`,  with the following information is needed.
 
-## Usage
+```
+  host: test.salesforce.com
+  username: username@domain
+  password: xxxxxxxxxxxxxxxxxxxxx
+  security_token: xxxxxxxxxxxxx
+  client_id: xxxxxxxxxxxxxxxxxxxx
+  client_secret: xxxxxxxxxxxxxx
+  api_version: '24.0'
+```
 
-TODO: Write usage instructions here
+Please refer to [https://github.com/ejholmes/restforce](https://github.com/ejholmes/restforce) for the detail.
 
 ## Contributing