Update get-started-create-site-design.md

Updated use section to reference Invoke to apply to existing site collection

Author: seansquires

docs/declarative-customization/get-started-create-site-design.md

@@ -1,7 +1,7 @@
 ---
 title: Get started creating SharePoint site designs and site scripts
 description: Create site designs to provide reusable lists, themes, layouts, pages, or custom actions so that your users can quickly build new SharePoint sites with the features they need. 
-ms.date: 04/20/2018
+ms.date: 07/27/2018
 ---
 
 # Get started creating site designs and site scripts
@@ -113,7 +113,9 @@ The REST API to add a new site design is **CreateSiteDesign**.
 
 ## Use the new site design
 
-Now that you've added a site script and site design, you can use it to create new sites.
+Now that you've added a site script and site design, you can use it to create new sites through the self-service site creation experience or apply the site design to an existing site using the **Invoke-SPOSiteDesign** command in PowerShell.
+
+### New site creation
 
 1. Go to the home page of the SharePoint site that you are using for development. 
 
@@ -133,6 +135,12 @@ Now that you've added a site script and site design, you can use it to create ne
 
 9. You will see the custom list on the page. 
 
+### Apply to an existing site collection
+
+You can also apply a published site design to an existing site collection using the [Invoke-SPOSiteDesign](https://docs.microsoft.com/en-us/powershell/module/sharepoint-online/Invoke-SPOSiteDesign?view=sharepoint-ps) cmdlet. 
+
+You can already apply to Group-connected Team and Communication sites. By August 2018 you will also be able to apply site designs to the team site not connected to an Office 365 Group, a classic team site, or a classic publishing site.
+
 ## See also
 
-- [SharePoint site design and site script overview](site-design-overview.md)
+- [SharePoint site design and site script overview](site-design-overview.md)