How to create a certificate/privkey and sign a SiS package for Symbian phones(Obsolete,needs update)

Credits for this information go to this site. Although it is dedicated to the Nokia N91 phone, following the instructions has allowed me to succesfully sign and install my SiS files on a Nokia N80 phone. I suppose it works for other models too.
Download and Install the following packages:
Developer Certificate Request Tool for Symbian
Sign SiS [...]