To install this Icinga for Windows component, you can use the official Icinga repositories. You can read more about this on how to install components for adding existing repositories or create own repositories.
You should always stick to one way of installing/updating any modules for the Icinga for Windows solution. It is not supported and not recommended to mix different installation methods.
Install-IcingaComponent -Name 'plugins';Install-IcingaComponent -Name 'plugins' -Snapshot;Update-Icinga -Name 'plugins';Update-Icinga -Name 'plugins' -Snapshot;