[DOCS] Add new section to configure-monasca-agent.rst

New section added for adding the compute hosts that needs to be
monitored in user's OSA infrastructure.

Change-Id: I11eee6349625a8999ddf733f83b93acf6b71e308

doc/source/configure-monasca-agent.rst

@@ -14,13 +14,36 @@ collecting metrics from a variety of sources.
 The Agent is extensible through configuration of additional check
 and setup plugins, written in Python.
 
+Configuring target hosts
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Modify ``/etc/openstack_deploy/conf.d/monasca.yml`` by adding a list of
+``monasca-agent-infra_hosts``, containing all the hosts that needs to
+be monitored:
+
+In ``monasca.yml``:
+
+   .. code-block:: yaml
+
+       [...]
+
+       monasca-agent-infra_hosts:
+         infra01:
+           ip: INFRA01_IP_ADDRESS
+         infra02:
+           ip: INFRA02_IP_ADDRESS
+         infra03:
+           ip: INFRA03_IP_ADDRESS
+
+
+Replace ``*_IP_ADDRESS`` with the IP address of the br-mgmt container
+management bridge on each target host.
+
 Setting up monasca-agent
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
-The monasca-agent playbook targets all hosts and containers. In that
-way, to install monasca-agent no configuration is necessary, simply
-build the monasca-agent packages/virtual environmnet (if not built
-already) and run its playbook:
+Build the monasca-agent packages/virtual environment (if not
+built already) and run its playbook:
 
    .. code-block:: console