ssh/sftp the update zip to a datastore of your choice. I usually use CoreFTP LE as my client and push the update to /vmfs/volumes/1A-LabsESXiDataStore-Thick/ISO-Bits-Drivers/
Put the host into maintenance mode using vcenter/vsphere web interface or use Kitty/Putty to do it via the cmdline.
# vim-cmd hostsvc/maintenance_mode_enter
Change to the location where you uploaded the update and start the update.
# esxcli software vib update -d “/vmfs/volumes/1A-LabsESXiDataStore-Thick/ISO-Bits-Drivers/update-from-esxi5.5-5.5_update02.zip”
Optionally, you can view the installed files. check the dates for the particular update being applied.
#esxcli software vib list
It will require a reboot to complete the update.
Finally, exit mainenace mode and you’re back in business.
# vim-cmd hostsvc/maintenance_mode_exit
A full list of vCenter updates is maintained here: http://vsphere-land.com/vinfo/release-build-info