Updated docs for creating grafyaml key

There was some confusion around installing grafana dashboards since
the move to grafyaml, tried to update the docs to make it further clear
about steps needed.

Change-Id: I536a82b1d9800e9a648ef3d5e67a1437f097ff2a
Closes-Bug: #1757545

Author: aakarshg

doc/source/installation.rst

@@ -113,11 +113,14 @@ you deploy with aggregation.
 
 Browbeat uses Grafyaml to upload dashboards to Grafana. Grafyaml is installed by browbeat
 at the location pointed to by the variable `browbeat_venv` in `ansible/install/group_vars/all.yml`.
-So, you need to first run the browbeat install playbook `ansible/install/browbeat.yml` before running
-the below playbook.
+To upload dashboards, the api key is required which can be generated by following instructions at
+http://docs.grafana.org/http_api/auth/#create-api-token
 
 ::
 
+  [stack@ospd ansible]$ # update the vars and make sure to update grafana_apikey with value
+  [stack@ospd ansible]$ vi install/group_vars/all.yml
+  [stack@ospd ansible]$ ansible-playbook -i hosts install/browbeat.yml # if not run before.
   [stack@ospd ansible]$ ansible-playbook -i hosts install/grafana-dashboards.yml
 
 Not mantained (Pre-Pike): Run Overcloud checks