Add First login steps back into Kibana doc

Kolla-ansible version 4.0.0 contained the steps to follow when logging
in to Kibana for the first time.

These got deleted when the process was seemingly automated, but the
relevant machinery no longer works. See [1] as well.

Backport to Ussuri, Train, Stein (possibly more).

[1] https://review.opendev.org/726289

Change-Id: If65622dc78e7f8fd16e37ee31bc9f34eb9267549

doc/source/reference/logging-and-monitoring/central-logging-guide.rst

@@ -47,6 +47,21 @@ After successful deployment, Kibana can be accessed using a browser on
 The default username is ``kibana``, the password can be located under
 ``<kibana_password>`` in ``/etc/kolla/passwords.yml``.
 
+First Login
+-----------
+
+When Kibana is opened for the first time, it requires creating a default index
+pattern. To view, analyse and search logs, at least one index pattern has to
+be created. To match indices stored in ElasticSearch, we suggest using the
+following configuration:
+
+#. Index pattern - flog-*
+#. Time Filter field name - @timestamp
+#. Expand index pattern when searching [DEPRECATED] - not checked
+#. Use event times to create index names [DEPRECATED] - not checked
+
+After setting parameters, one can create an index with the *Create* button.
+
 Search logs - Discover tab
 --------------------------