chore: add instructions how to get started

README.md

@@ -10,8 +10,28 @@ Red Hat OpenShift application deployment examples.
   - view          # A demo service that displays the random number
 ```
 
+## Prerequisites
+
+- OpenShift >= 4.17 cluster
+- Enabled GitOps subscription in the OpenShift cluster (ArgoCD)
+- `oc` CLI installed and configured to access the OpenShift cluster
+
 ## How to deploy
 
+Before we can deploy any of the services, we need to modify our central ArgoCD management application to allow sourcing `Application` resources from other than the `openshift-gitops` namespace. This is necessary because the services are deployed in a separate project, namespace and ArgoCD application.
+
+To do this, execute the following patch command:
+
+```bash
+oc -n openshift-gitops patch argocds.argoproj.io openshift-gitops \
+  --type merge \
+  --patch '{"spec":{"sourceNamespaces":["openshift-gitops","example-application-basic","example-application-progressive"]}}'
+```
+
+The `openshift-gitops` namespace is the `default` namespace and might not be necessary to add to the `sourceNamespaces` list. However, it is added here for completeness.
+
+### Deploy the services
+
 1. Clone the repository
 
 ```bash