Update Instructions to Install Chart from source (apache#15868)

The INSTALL file should contain details to run chart from source not other repo. This PR fixes it for Helm Chart Release.

chart/INSTALL

@@ -1,14 +1,14 @@
 ## INSTALL / BUILD instructions for Apache Airflow Chart
 
 # The Assumption here is that you have a running Kubernetes cluster
-# with helm installed
+# and helm installed & configured to talk with the cluster
 
-### Add Airflow Helm Repo
-helm repo add apache-airflow https://airflow.apache.org
-helm repo update
+# Run `helm install` Command
+helm install airflow .
 
-### Update Chart Dependencies
-helm dep update
+# If you want to install in a particular namespace
+## Create that namespace (example 'airflow' here, change it as needed)
+kubectl create namespace airflow
 
-### Run `helm install` Command
-helm install airflow apache-airflow/airflow
+## Install the chart in that namespace
+helm install airflow -n airflow .