Add Root URL info under License file management (#24712)

* Add Root URL info under License file management

Edited through GitHub, not tested on development web server.

* Update docs/sources/enterprise/_index.md

Make updating root_url instructions more straightforward, with action first and explanation second.

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Update docs/sources/enterprise/_index.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Update docs/sources/enterprise/_index.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

docs/sources/enterprise/_index.md

@@ -86,3 +86,22 @@ license_path = /company/secrets/license.jwt
 ```
 
 This setting can also be set with an environment variable, which is useful if you're running Grafana with Docker and have a custom volume where you have placed the license file. In this case, set the environment variable `GF_ENTERPRISE_LICENSE_PATH` to point to the location of your license file.
+
+### Root URL
+
+Update the [`root_url`](../installation/configuration/#root-url) in your configuration. It should be the URL that users type in their browsers to access the frontend, not the node hostname(s).
+
+This is important, because as part of the validation checks at startup, Grafana compares the license URL to the [`root_url`](../installation/configuration/#root-url) in your configuration. 
+
+In your configuration file:
+
+```
+[server]
+root_url = https://grafana.blah.com/
+```
+
+Or with an environment variable:
+
+```
+GF_SERVER_ROOT_URL=https://grafana.blah.com/
+```