Hi We all know that Microsoft introduced Look book themes for new modern sites for design guidance. So generally if you have tenant Admin permissions you can apply those themes to new site collection but when you are applying to existing site collections. It will not allow us.

Can’t add this template
The provided site is already in use and the current template cannot be provisioned onto an already existing site. Please provide a different url.

So how to proceed now. To rescue us PnP PowerShell comes into action.
In PnP Powershell Online we have few commands to extract the design theme from the site which is applied with Look Book theme and later we can apply that to our existing site collection. Here the condition is both sites must be of same type. Say for example both must be Communication sites.

Lets start…

  1. We need to open PowerShell Online Management Shell or Windows PowerShell ISE in administrator mode.
    Generally I Prefer Windows PowerShell ISE in administrator mode.
  2. Now we need to Install SharePoint PnP PowerShell Online.

Install-Module SharePointPnPPowerShellOnline

cmdlet

3. Lets now connect to the site where we already applied a Look book theme. You can read my previous article on how to apply Look Book theme to new site Collection.

Here In this post I applied the Leadership Connection theme. You can get this here: https://lookbook.microsoft.com/details/c19f437b-35ca-42f2-b27a-1caa49ad8bde

Connect-PnPOnline -Url “https: //abcxyz.sharepoint.com/sites/Sourcesite”

cmdlet

4.It will prompt a popup to enter credentials for the site. Please enter them correctly.

5. After entering credentials. Get the source site template with below cmdlet.

Get-PnPProvisioningTemplate -Out “D:\SourceSiteTemplate.xml”

cmdlet

6. So now let the extraction process happen and save the xml file in D Drive . Dont give C Drive sometimes access problems may come.

7. Go to D drive and check the xml file.

8.Now connect with the destination site which is already existing communication site in your tenant. Same PnP command.

Connect-PnPOnline -Url “https: //abcxyz.sharepoint.com/sites/DestinationSite”

Pnp cmdlet

9. Once after connecting successfully enter the cmdlet to Apply the theme to destination site from D drive.

Apply-PnPProvisioningTemplate -Path “D:\SourceSiteTemplate.xml”

PnP cmdlet

10.You can see the process of applying the extracted template in action.

11. If it is first time it will ask for the consent to few rules.

12. Accept those permissions.

13. Finally the lookbook theme will be applied to the existing communication site.

14. Only thing to remember is source and destination sites must be of same type here I took Communication sites.

15. Now ends the extraction and apply of lookbook themes on existing sites.

Watch this whole procedure in Action