[DOCS-1127] Write App UI landing page (#1268)

[DOCS-1127] Write App UI landing page
---------
Co-authored-by: Noah Luna <15202580+ngrayluna@users.noreply.github.com>

Author: mdlinville

content/guides/models/app/_index.md

@@ -3,9 +3,25 @@ menu:
   default:
     identifier: w-b-app-ui-reference
     parent: models
-title: W&B App UI Reference
+title: W&B App UI
 url: guides/app
 aliases:
 - /guides/models/app/features
 ---
 
+This section provides details to help you use the W&B App UI. Manage workspaces, teams, and registries, visualize and observe experiments, create panels and reports, configure automations, and more.
+
+Access the W&B App in a web browser. 
+
+- A W&B Multi-tenant deployment is accessible on the public web at https://wandb.ai/.
+- A W&B Dedicated Cloud deployment is accessible at the domain you configured when you signed up for W&B Dedicated Cloud. An admin user can update the domain in the W&B Management Console. Click on the icon in the top right corner and then click **System console**.
+- A W&B Self-Managed deployment is accessible at the hostname you configured when you deployed W&B. For example, if you deploy using Helm, the hostname is configured in `values.global.host`. An admin user can update the domain in the W&B Management Console. Click on the icon in the top right corner and then click **System console**.
+
+Learn more:
+
+- [Track experiments]({{< relref "/guides/models/track/" >}}) using runs or sweeps.
+- [Configure deployment settings]({{< relref "settings-page/" >}}) and [defaults]({{< relref "cascade-settings.md" >}}).
+- [Add panels]({{< relref "panels/" >}}) to visualize your experiments, such as line plots, bar plots, media panels, query panels, and tables.
+- [Add custom charts]({{< relref "custom-charts/" >}}).
+- [Create and share reports]({{< relref "/guides/core/reports/" >}}).
+