Enable metrics requirement

Hi everyone, I turn to the forum because it seem impossible to get more detail info on how to enable metrics on a cluster in rancher 2.4.8

kubernetes cluster v1.18.8
ubuntu 20lts 3vcpu 4gb ram: rancher only
ubuntu 20lts 8vpcu 12gb ram: etcd-control plane
windows 2019 6vcpu 12gb ram: worker

Virtualization env: vmware

Everything seems fine all is green but when I try to enable live metrics to the cluster I get this message:

What I would like to know is how to messure those millicpu and why is asking for more ram, wich node I need to upgrade to get metrics.
It seems so easy but there is a lack of information out there

Thanks in advance