Hi, give this a shot:
1.) browse to where you extracted your cake installation to
2.) if you see folders called "app", "cake", "docs" and "vendors" then you are in the right place
3.) go into "app" directory and then into the "config" subdirectory
4.) one of the files here should be called "core.php"
5.) open this file in your text editor, search for the line "Security.salt"
6.) replace the value (which looks something like "fd60aeda2c2b877892d4cddd635a437b4892c63a") with one of your own
It doesn't really matter what it is, as long as it's not easy to guess. You could use an online SHA1 hash generator tool (e.g.
http://www.md5.br-design.co.uk/) to generate a new crazy long key like what is there by default.
Hope this helps.