README.md in twoffein-client-0.1.1 vs README.md in twoffein-client-0.1.2

@@ -40,9 +40,16 @@
     profile - List the profile, which you have chosen by PROFILE
     tweet   - Tweet your drinking DRINK
 
 ```
 
+### Credentials
+
+You need your credentials (screen_name, api_key) to get access to the Twoffein-API. Please set these as
+shell environment variables `TWOFFEIN_SCREEN_NAME` and `TWOFFEIN_API_KEY`. Thank's!
+
+    TWOFFEIN_SCREEN_NAME=NAME TWOFFEIN_API_KEY=KEY twoffein-client drinks
+
 ## Examples
 
 
 ### Drinks