[Q] [HELP] Extracting a Stock ROM for modify it topic

Hello everyone.
I want to create my own Custom ROM. I want to make it based on Stock ROM, but I don't know how to extract it.
I downloaded the firmware from SamMobile, extracted the .tar.md5 file with 7-Zip and got the *.img files.
I read some guides about how to use Android Kitchen but I don't know how to start with the Stock ROM to make my ROM based on it, and then, use the Kitchen.
Sorry for my English.
Thanks in advance.
Greetings!