Update SMS Broadcast instructions

Author: pwseg

src/engage/campaigns/broadcasts.md

@@ -47,7 +47,10 @@ Follow these steps to create an email broadcast:
     - To send a message to a pre-built audience, choose `Part of an Audience`, then select the audience.
     - To exclude users from the audience, click **Add condition** in the **And who** section. Click **And who**, then select **And not who**. Segment will exclude users from the audience you choose.
 5. Click **Preview** to estimate the audience size.
-7. Select **Build**.
+6. Select **Build**
+7. Choose an existing template or create a new template.
+    - You can edit existing templates. Edited templates won't be saved in the content tab.
+    - If you create a new template, enter a name, then select the language and content type.
 8. Choose a messaging service, enter your message into the body field, and add any merge tags. 
     - (Optional:) Test your SMS.
     - Include opt out instructions; your SMS broadcast must contain `Reply STOP to unsubscribe`.