Hmm. I've never even heard of this utility but the website seems clear enough to me.
Go here:
http://www.serialz.to/s2kupdates.html
Look under 'half year updates' and download the 4th file down (396kB). Unzip this file. Double-click on the file with the 'seu' extension. Your program will now be 6 months closer to being up to date than it was before. (I only know that because I've just unzipped the downloaded file and read the text file which is there).
Repeat for the third file down the list (321kB), then the second (362kB) and finally the file at the top of the list (337kB).
Your program is now up to date. In future, either update every fortnight, using the files in the top list, or wait for 6 months for a new file to appear at the top of the half-yearly list.
Chris