Update README.md

Author: waprin

monitoring/v3/README.md

@@ -10,25 +10,43 @@ write a TimeSeries value to it.
 
     * [Maven 3](https://maven.apache.org)
 
+# Set Up Your Local Dev Environment
 
-Go to the [Google Developers Console](https://console.developer.google.com).
+Create local credentials by running the following command and following the oauth2 flow:
 
-    * Go too API Manager -> Credentials
-    * Click ['New Credentials', and create a Service Account](https://console.developers.google.com/project/_/apiui/credential/serviceaccount)
-     Download the JSON for this service account, and set the
-     `GOOGLE_APPLICATION_CREDENTIALS` environment variable to point to the file
-     containing the JSON credentials.
+    gcloud beta auth application-default login
+    
+To run:
+    * `mvn clean install`
+    * `./list_resources_example.sh <YOUR-PROJECT-ID>
+    * `./run_custom_metrics.sh <YOUR-PROJECT-ID>    
 
-    ```
-    export GOOGLE_APPLICATION_CREDENTIALS=~/Downloads/<project-id>-0123456789abcdef.json
-    ```
+## Running on GCE, GAE, or other environments
 
-# Set Up Your Local Dev Environment
+On Google App Engine, the credentials should be found automatically.
 
-To run locally:
-    * `mvn clean install`
-    * `./list_resources_example.sh <YOUR-PROJECT-ID>
-    * `./run_custom_metrics.sh <YOUR-PROJECT-ID>
+On Google Compute Engine, the credentials should be found automatically, but require that
+you create the instance with the correct scopes. 
+
+    gcloud compute instances create --scopes="https://www.googleapis.com/auth/cloud-platform,https://www.googleapis.com/auth/compute,https://www.googleapis.com/auth/compute.readonly" test-instance
+
+If you did not create the instance with the right scopes, you can still upload a JSON service 
+account and set GOOGLE_APPLICATION_CREDENTIALS as described below.
+
+## Using a Service Account
+
+In non-Google Cloud environments, GCE instances created without the correct scopes, or local
+workstations if the `gcloud beta auth application-default login` command fails, use a Service 
+Account by doing the following:
+
+* Go to API Manager -> Credentials
+* Click 'New Credentials', and create a Service Account or [click  here](https://console.cloud.google
+.com/project/_/apiui/credential/serviceaccount)
+ Download the JSON for this service account, and set the `GOOGLE_APPLICATION_CREDENTIALS`
+ environment variable to point to the file containing the JSON credentials.
+
+
+    export GOOGLE_APPLICATION_CREDENTIALS=~/Downloads/<project-id>-0123456789abcdef.json
 
 ## Run Tests