help flash unlock se k550im

Here is a tutorial:

Flash your phone and How to apply or remove patch using SETool 2 Lite - Top Sony Forums

I'm sorry I could not be of more assistance because I am not familiar with Setool2lite. I can tell you though that you can get all the files you will need here at TopSONY:

Top Sony - Download

The MAIN and FS will be under the firmware section and the custpacks (also known as customization) will be found in the "Custom files" section.

Best of luck to you!:)