To enable SNMP on VMWare VCenter Appliance, for monitoring, first SSH to Vcenter Appliance with an authorised user (like root). At the Command prompt (not shell) SNMPv1/v2c can be configured using the following commands.

Get the current SNMP config:

Command> snmp.get

Set the SNMP Community string:

snmp.set --communities public,secretcommunitystring

Set the device location:

snmp.set --syslocation London

Optionally set up users:

snmp.set --users userid/authhash/privhash/security

(example) snmp.set --users test/-/-/none

snmp.hash  --auth_hash secret1 --priv_hash secret2

Finally Enable SNMP:

snmp.enable

More information @ VMWare Docs: Configure ESXi for SNMPv1 and SNMPv2c - https://docs.vmware.com/en/VMware-vSphere/6.7/com.vmware.vsphere.monitoring.doc/GUID-2A8FC3DC-53C3-4245-A4CF-CC5C7935D04B.html