Document broadcast messages in UI

doc/administration/index.md

@@ -54,6 +54,7 @@ Learn how to install, configure, update, and maintain your GitLab instance.
 - [Third party offers](../user/admin_area/settings/third_party_offers.md)
 - [Compliance](compliance.md): A collection of features from across the application that you may configure to help ensure that your GitLab instance and DevOps workflow meet compliance standards.
 - [Diff limits](../user/admin_area/diff_limits.md): Configure the diff rendering size limits of branch comparison pages.
+- [Broadcast Messages](../user/admin_area/broadcast_messages.md): Send messages to GitLab users through the UI.
 - [Elasticsearch](../integration/elasticsearch.md): Enable Elasticsearch to empower GitLab's Advanced Global Search. Useful when you deal with a huge amount of data. **[STARTER ONLY]**
 - [External Classification Policy Authorization](../user/admin_area/settings/external_authorization.md) **[PREMIUM ONLY]**
 - [Upload a license](../user/admin_area/license.md): Upload a license to unlock features that are in paid tiers of GitLab. **[STARTER ONLY]**

doc/user/admin_area/broadcast_messages.md

+# Broadcast Messages
+
+GitLab can display messages to all users of a GitLab instance in a banner that appears in the UI.
+
+![Broadcast Message](img/broadcast_messages.png)
+
+NOTE: **Note:**
+If more than one banner message is active at one time, they are displayed in a stack in order of creation.
+
+## Adding a broadcast message
+
+To display messages to users on your GitLab instance, add broadcast message.
+
+To add a broadcast message:
+
+1. Navigate to the **Admin Area > Messages** page.
+1. Add the text for the message to the **Message** field. Markdown and emoji are supported.
+1. If required, click the **Customize colors** link to edit the background color and font color of the message.
+1. Select a date for the message to start and end.
+1. Click the **Add broadcast message** button.
+
+NOTE: **Note:**
+Once a broadcast message has expired, it is no longer displayed in the UI but is still listed in the
+list of broadcast messages.
+
+## Editing a broadcast message
+
+If changes are required to a broadcast message, they can be edited.
+
+To edit a broadcast message:
+
+1. Navigate to the **Admin Area > Messages** page.
+1. From the list of broadcast messages, click the appropriate button to edit the message.
+1. After making the required changes, click the **Update broadcast message** button.
+
+TIP: **Tip:**
+Expired messages can be made active again by changing their end date.
+
+## Deleting a broadcast message
+
+Broadcast messages that are no longer required can be deleted.
+
+To delete a broadcast message:
+
+1. Navigate to the **Admin Area > Messages** page.
+1. From the list of broadcast messages, click the appropriate button to delete the message.
+
+Once deleted, the broadcast message is removed from the list of broadcast messages.
+
+NOTE: **Note:**
+Broadcast messages can be deleted while active.