integration-docs: Update Discourse for new doc format.

Part of zulip#29592.

templates/zerver/integrations/discourse.md

@@ -1,16 +1,38 @@
-1.  {!create-an-incoming-webhook.md!}
+# Zulip Discourse integration
 
-    The API keys for "Incoming webhook" bots are limited to only
+Forward new Discourse posts to Zulip!
-    sending messages via webhooks. Thus, this bot type lessens
-    the security risks associated with exposing the bot's API
-    key to third-party services.
 
-1.  Copy the `USERNAME` and `API KEY` - you'll need it later.
+{start_tabs}
 
-1.  Head over to the
+1. {!create-an-incoming-webhook.md!}
-    [discourse-chat-integration setup instructions](https://meta.discourse.org/t/68501)
-    and complete them.
 
-{!congrats.md!}
+1. Install the Discourse [Chat Integration][chat-integration].
 
-![Discourse chat integration](/static/images/integrations/discourse/001.png)
+1. In your **Discourse site settings**, toggle
+   `chat_integration_zulip_enabled`, and fill in the following information:
+
+    * `chat_integration_zulip_server`: {{ zulip_url }}
+    * `chat_integration_zulip_bot_api_key`: your bot's API key
+    * `chat_integration_zulip_bot_email_address`: your bot's email
+
+1. Go to the **Plugins** tab, click on **Chat Integration**. Select
+   **Zulip**, and click **Add Channel**.
+
+1. Set **Stream** to the [channel](/help/create-a-channel) name that you'd
+   like to receive notifications in, set **Subject** to the topic name, and
+   click **Save Channel**.
+
+1. To filter the posts you'd like to forward to Zulip,
+   [configure the rules][configuring-rules] in your Discourse forum's
+   **Chat Integrations** panel.
+
+{end_tabs}
+
+### Related documentation
+
+- [Discourse Chat Integration][chat-integration]
+- [Discourse's documentation on the Zulip integration][setup-instructions]
+
+[setup-instructions]: https://meta.discourse.org/t/68501
+[chat-integration]: https://meta.discourse.org/t/discourse-chat-integration/66522
+[configuring-rules]: https://meta.discourse.org/t/discourse-chat-integration/66522#configuring-rules-4