Update README.md

README.md

@@ -1,4 +1,51 @@
 grails-spring-security-oauth-facebook
-=====================================
+====================================
 
-Facebook support for Grails Spring Security OAuth.
+Facebook extension for [Grails Spring Security OAuth][spring-security-oauth-plugin] plugin
+
+Installation
+------------
+
+Add the following plugin definition to your BuildConfig:
+```groovy
+// ...
+plugins {
+  // ...
+  compile ':spring-security-oauth:2.0.2'
+  compile ':spring-security-oauth-facebook:0.1'
+  // ...
+}
+```
+
+Usage
+-----
+
+Add to your Config:
+```groovy
+oauth {
+  // ...
+  providers {
+    // ...
+    facebook {
+      api = org.scribe.builder.api.FacebookApi
+      key = 'oauth_facebook_key'
+      secret = 'oauth_facebook_secret'
+      successUri = '/oauth/facebook/success'
+      failureUri = '/oauth/facebook/error'
+      callback = "${baseURL}/oauth/facebook/callback"
+    }
+    // ...
+  }
+}
+```
+
+In your view you can use the taglib exposed from this plugin and from OAuth plugin to create links and to know if the user is authenticated with a given provider:
+```xml
+<oauth:connect provider="facebook" id="facebook-connect-link">Facebook</oauth:connect>
+
+Logged with facebook?
+<s2o:ifLoggedInWith provider="facebook">yes</s2o:ifLoggedInWith>
+<s2o:ifNotLoggedInWith provider="facebook">no</s2o:ifNotLoggedInWith>
+```
+
+[spring-security-oauth-plugin]: https://github.com/enr/grails-spring-security-oauth