How to monitor VCenter/ESXi/VMs

Excellent article

But I have a problem with its definitions.
It states

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You must have defined the ESXi-server as the host in Checkmk, and configured it as an agent (Checkmk Agent).

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I am unsure as how can I configure host as an agent?
Haven’t found such option in host properties.

Also, the same document states that

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Once the prerequisites have have been satisfied you can create a Rule in the Setup > VM, Cloud, Container > VMWare ESX via vSphere rule set. This will be assigned to the defined host, so that instead of the standard agent the special agent will be used for retrieving data from the VMware-monitoring.

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BUT I can not find - where are those special agents located?