Hi mini,
Sorry, I'm in a bit of a rush, but am sure someone will answer more fully in due course.
What make and model of phone do you have? If it's not a Nokia or certain Sony Ericssons, then it's likely it's not running the Symbian OS anyway. If it is one of those, what you need is the relevant PC software for your phone. eg. For Nokia, this is Nokia PC Suite. Go to your phone manufacturer's website to download. Install this and connect phone as per the instructions and you should then be able to transfer the .sis file to your phone using the relevant tool within the package.
Hope that's of some use, if not very comprehensive due to time.
