Enable SNMP in vSphere ESX 6

Manually via SSH:
esxcli system snmp set -r
esxcli system snmp set -c m0nkeys33
esxcli system snmp set -p 161
esxcli system snmp set -L “The Bunker, Newbury”
esxcli system snmp set -C support@cloudmonkey.co.uk
esxcli system snmp set -e yes

PowerCLI to all hosts:
Via this PowerShell script courtesy of 9to5it.com 

Host Profiles
Edit an existing profile under SNMP and apply to host/cluster.
* Host(s) need to be in maintenance mode in order to apply the host policy.