I will suggest you to go through the Installation guide (page 20) which talks about ePO upgrade.
In addition to this, I will suggest you to go through Master KB article KB#:KB60569.
Make sure that Autoclose is set to False as per KB#:KB66879.
Make sure that you backup the database and below folders before running the patch setup.
...\Program Files\McAfee\ePolicy Orchestrator\DB\ (default installation path for ePO 4.0)
...\Program Files\McAfee\ePolicy Orchestrator\Server\Extensions\ (default installation path for software extensions)
...\Program Files\McAfee\ePolicy Orchestrator\Server\Conf\Catalina\ (default path for required files used by software extensions)
...\Program Files\McAfee\ePolicy Orchestrator\Server\Keystore\ (default path for server certificates
Rest of the suggestions will be after looking the log files once patch installation is failing.