add notes about fleet server and apm integration in fleet-managed get…

…ting started guide (#4714)

(cherry picked from commit 33da1d1)

docs/en/observability/apm/getting-started-apm/get-started-with-fleet-apm-server.asciidoc

@@ -15,8 +15,15 @@ include::{ingest-docs-root}/docs/en/ingest-management/tab-widgets/prereq.asciido
 == Step 1: Set up Fleet
 
 Use {fleet} in {kib} to get APM data into the {stack}.
-The first time you use {fleet}, you'll need to set it up and add a
-{fleet-server}:
+
+[NOTE]
+====
+If you already have a {fleet-server} set up, you can choose to skip this step.
+====
+
+The first time you use {fleet}, you'll need to set it up and add a {fleet-server} using the
+steps outlined below.
+
 
 include::{ingest-docs-root}/docs/en/ingest-management/tab-widgets/add-fleet-server/content.asciidoc[tag=self-managed]
 
@@ -26,6 +33,13 @@ For more information, refer to {fleet-guide}/fleet-server.html[{fleet-server}].
 [[add-apm-integration]]
 == Step 2: Add and configure the APM integration
 
+[NOTE]
+====
+If you don't have a {fleet} setup already in place, the easiest way to get started
+is to run the APM integration in the same {agent} that acts as the {fleet-server}.
+However, it is _not mandatory_ for the APM integration to run in the same {agent} that acts as the {fleet-server}.
+====
+
 include::{observability-docs-root}/docs/en/observability/tab-widgets/add-apm-integration/content.asciidoc[tag=self-managed]
 
 ****