[DOCS] Update add node section (#89393) (#89618)

* [DOCS] Update add node section

* Include information for enrolling nodes

Author: Adam Locke

docs/reference/setup/add-nodes.asciidoc

@@ -25,21 +25,21 @@ green.
 
 image::setup/images/elas_0204.png["A cluster with three nodes"]
 
-You can run multiple nodes on your local machine in order to experiment with how
-an {es} cluster of multiple nodes behaves. To add a node to a cluster running on
-your local machine:
-
-. Set up a new {es} instance.
-. Specify the name of the cluster with the `cluster.name` setting in
-`elasticsearch.yml`. For example, to add a node to the `logging-prod` cluster,
-add the line `cluster.name: "logging-prod"` to `elasticsearch.yml`.
-. Start {es}. The node automatically discovers and joins the specified cluster.
-
-To add a node to a cluster running on multiple machines, you must also
-<<unicast.hosts,set `discovery.seed_hosts`>> so that the new node can discover
+[discrete]
+=== Enroll nodes in an existing cluster
+You can enroll additional nodes on your local machine to experiment with how an
+{es} cluster with multiple nodes behaves. 
+
+[NOTE]
+====
+To add a node to a cluster running on multiple machines, you must also set
+<<unicast.hosts,`discovery.seed_hosts`>> so that the new node can discover
 the rest of its cluster.
+====
+
+include::../../../x-pack/docs/en/security/enroll-nodes.asciidoc[]
 
-For more information about discovery and shard allocation, see
+For more information about discovery and shard allocation, refer to
 <<modules-discovery>> and <<modules-cluster>>.
 
 [discrete]