Updated Quick Start doc to include GCP env variables

docs/book/src/user/quick-start.md

@@ -463,6 +463,19 @@ export SERVICE_DOMAIN="k8s.test"
 {{#/tab }}
 {{#tab GCP}}
 
+
+```bash
+# Name of the GCP datacenter location. Change this value to your desired location
+export GCP_REGION="<GCP_REGION>"
+export GCP_PROJECT="<GCP_PROJECT>"
+# Make sure to use same kubernetes version here as building the GCE image
+export KUBERNETES_VERSION=1.20.9
+export GCP_CONTROL_PLANE_MACHINE_TYPE=n1-standard-2
+export GCP_NODE_MACHINE_TYPE=n1-standard-2
+export GCP_NETWORK_NAME=<GCP_NETWORK_NAME or default>
+export CLUSTER_NAME="<CLUSTER_NAME>"
+```
+
 See the [GCP provider] for more information.
 
 {{#/tab }}