Hi there, welcome to McAfee community.
Here are some helpful ePO 5.3.3 links. You definitely want to read the release notes. The upgrade process is very straightforward. You simply run the installer and it will upgrade. Please take a DATABASE backup prior to the upgrade. If you are in a virtual environment, you may want to take a snapshot temporarily also.
Thanks Moe, given the install was quite large I wanted to make sure that I had checked prereqs, product compatibility etc. before upgrade, the pre upgrade auditor did a good job at that but I'm old school and like to see the documentation too.
Thanks for your help, upgrade done, all good.