You will need to download New Firmware (Main,FS and Custpack)*
You have to flash your phone with the new firmware first, before you can unlock it, because you have to use the same Main firmware file to unlock it.
I would use SEtool, it seems easier to use.
Make sure your phone is fully charged or you will have all sorts of problems.
* I found for 2 euros, that this site have what you need.

PS- Make sure That all the MAIN and FS firmware files are the same country. (They all support english)