The link you gave appears bad. The GPO templates should be available on Win11 machines running the latest updates. Note that the template is very much preview and some of the options may or may not work as it evolves.
If you're trying to define the policy on a DC that doesn't support the template yet you'll need to import the template definition first. On a WIn11 machine where the template is available. Then go to C:\Windows\PolicyDefinitions
. The current template is, I believe, Windowscopilot.admx
. You'll also need to grab the locale-specific version under the folders of the locales you support.
On the DC open the GPO editor and then go to the Administrative Templates section and import the ADMX files. You should then see the options.
Remember that this is in preview, just because a policy is defined doesn't mean it will work on all machines. Specifically I believe you have to be running the latest Win11 update and potentially be a Copilot+PC machine before they take effect. I don't use it myself so I cannot confirm. But once you apply the template and force a GPO refresh it should be obvious.