1) how to configure it and send the syslogs to one server?
VMware KB: Configuring syslog on ESXi 5.x
Enabling syslog on ESXi 3.5 and 4.x (1016621)
2) Is there anyway to do it on the cluster level or it only can be done on individual VM?
It must be done at the ESXi host level, but you could look at things like Host Profiles to help.
