clarify and expand multiple api reference example

Author: devalog

fern/products/docs/pages/api-references/generate-api-ref.mdx

@@ -35,14 +35,50 @@ navigation:
 More on customizing your API Reference [here](/learn/docs/api-references/customize-api-reference-layout). 
 
 ### Include more than one API Reference
+
 To include multiple, distinct API definitions in your documentation, you can indicate which to include using the `api-name` property. The `api-name` corresponds to the name of the folder where your API definition is housed. 
 
+For example, your file structure might look like this:
+
+```bash
+fern/
+  ├─ fern.config.json 
+  ├─ docs.yml
+  ├─ plant-api/         
+  │   └─ api.yml     # API definition
+  └─ garden-api/          
+      └─ api.yml    # API definition
+```
+
+For a simple setup without tabs, you can include multiple API references directly in your navigation:
+
 ```yaml title="docs.yml"
 navigation:
   - api: Plant Store
-    api-name: plant-api
+    api-name: plant-api   # Matches folder name containing your API definition
   - api: Garden
-    api-name: garden-api
+    api-name: garden-api  # Matches folder name containing your API definition
 ```
 
+When using tabs, each API reference must be placed within a tab's `layout`:
 
+```yaml title="docs.yml" {12, 17}
+tabs:
+  plant-api:
+    display-name: Plant Store API
+    icon: leaf
+  garden-api:
+    display-name: Garden API
+    icon: tree
+navigation:
+  - tab: plant-api  # References the tab defined above
+    layout:
+      - api: Plant Store API
+        api-name: plant-api  # Matches folder name containing your API definition
+        skip-slug: true
+  - tab: garden-api  # References the tab defined above
+    layout:
+      - api: Garden API
+        api-name: garden-api  # Matches folder name containing your API definition
+        skip-slug: true
+```