Ibrahim,
Note that events will carry a timestamp from the device that generated them. That is independent of the time on the LMS server. If you want end-end times to be correct, use ntp everywhere.
Like devices, the LMS server itself can be ntp-synchronized.
For LMS on a physical Windows server, it's under the Control Panel - Date and Time setting.
If your Windows server is running as a VM you can use that method or alternatively use VMware tools to synchronize with the ESXi host which is in turn ntp-synchronized.
For LMS as a physical or soft appliance, it is a setting in the base configuration done from the cli, either at setup time of later. Here is the procedure:
http://www.cisco.com/en/US/customer/docs/net_mgmt/ciscoworks_lan_management_solution/4.2/install/guide/instl.html#wp1639616
For appliance-based systems, the server will need to be rebooted after changing the NTP server.
