Run it and follow instructions. The very important part is run BACKUP of your phone from it and make sure you backup all data especially in phone memory.
Follow its instructions. You need a fully charged battery, working USB2 connection cable and a reliable power source (Laptop, UPS all fine).
The important part is backup
If you have latest firmware installed, it will also offer "format" kind of thing and while you may want to do it, it is completely useless unless your phone memory is corrupted etc. That is Symbian, not windows.