improve "deploy existing containers" page

Author: commit111

docs/tutorials/deploy-container-using-the-cli.mdx

@@ -5,23 +5,48 @@ sidebar_position: 200
 
 # Deploy Existing Containers
 
-This example is useful if you already have a Docker container built manually or through a CI/CD system and have that the resulting image is available in a public or private repository accessible by Defang.
+This tutorial will show you how to deploy an existing container/multi-container application. 
+
+This example is rather useful if you already have a Docker container built manually, or through a CI/CD system where the resulting image is available in a public or private repository accessible by Defang.
+But it is not required in order to follow along to this tutorial. 
+
+# Step 1 - Make a Docker Compose file
+:::tip
+If you are unfamiliar with Docker Compose files, check out the [Compose](/docs/concepts/compose) page.
+:::
+Create a `compose.yaml` file to define the [service(s)](/docs/concepts/services) in your application.
+
+If you already have a Docker Compose file to define your service(s), you can use it directly and skip this step. 
 
-# Step 1 - Docker Compose
-If you already have a Docker Compose file for your service(s) you can use it directly. Else you can create one like this:
 
 ```yaml
 version: '3.9'
 services:
-  service1:
-    # This is just an example, replace with the image you want
-    image: "docker.io/nginx:latest"
+  web:
+    image: nginx:latest
     ports:
       - mode: ingress
         target: 3000		
+  app:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    ports:
+      - mode: ingress
+        target: 4000	
+  redis:
+    image: redis:6.2
+    restart: unless-stopped
+    ports:
+      - mode: host
+        target: 6379
 ```
 
+The example above shows a multi-container application with 3 services, `web`, `app`, `redis`.
+If you wanted to deploy only one container, say `app`, then the example would remain the same, except without the `web` and `redis` services.
+
 # Step 2 - Deploy
+Run the following command in the [Defang CLI]((/docs/getting-started#install-the-defang-cli.md)).
 ```text
 defang compose up
 ```