Moving this from Home & Home Office Help. It looks as if it belongs in Business/ePO.
Once ePO DAT is downloaded.
In the ePO server, Menu=>Software=>Master repository=>Check in package (select Product or update (.zip)), browser where ePO DAT is saved.
There are also video tutorials on the McAfee Service Portal that will guide you through some of the basics for ePO.
Follow the 'Video Tutorials' link.