The related Wiki-page (http://wiki.forum.nokia.com/index.ph...gn_Certificate) seems to be correct.
If you have HelloWorld.sis in the current directory (you write that you have created the .sis), you should type
into the command prompt, which will create test.key and test.cert (you have to help the random generator via moving the mouse vertically and/or typing random keypresses), then
makekeys -cert -dname "CN=kathyleong OU=home" test.key test.cert"
signs the .sis file.
signsis HelloWorld.sis HelloWorld.sisx test.cert test.key
Also note that if you have built the .sis file with Carbide, it is usually already signed.