Assuming the home/consumer edition here.
Double-click the taskbar icon (by the clock) or right-click it and select to open SecurityCenter
Click 'About' and the top right corner.
Often you will find it running behind the published DAT on the McAfee download page as it takes a while for updates to proliferate across the world's servers to all 40 million customers.
That's no reason for panic if the SecurityCenter is telling you all is well. Mine is Total Protection but the procedure is the same.
Free trials for the UK home products are here: http://home.mcafee.com/store/free-antivirus-trials
Note: With the upcoming 2012 editions now in beta testing, updates are handled differently and it wont be easy to check. We are awaiting word on that.
Not sure if the consumer version shares registry settings with the corporate version but if you want to test DAT levels by querying the registry then you could try the following key.
The DAT level is store as a hex value in this key