OK button.
Once you complete the steps, restart the Settings app, and then the option you were trying to configure should no longer appear grayed out.
If the related policy has not been configured, but it is causing the settings to be inaccessible, then try enabling and disabling the policy to see if that fixes the problem. If it does not work, it is possible that something happened with the feature in the Registry. In this case, you will need to research online (or ask in the Windows Central forums) for more specific details on how to change the settings for that particular feature.