How to apply archive .dif src?

[Agriias]

Good afternoon everyone!
First of all I am not good with English. But I will try to communicate this way using the google translator.

Second, people, I'm learning to start programming now and I don't really understand how to accomplish some things. I looked for help in channels of my own language, but people in it do not help and when they know, they want to charge to teach the person things that is just copy and paste a line from the notepad.

Could you ask me some questions?
I would like to modify my emulator's script but for myself I don't know how to start it. I read here in some forums that I can use a file called .di, but I don't like how I apply it to my soucer.

The dif in question is on this link: https://github.com/secretdataz/rathena/pull/8/files

for the content I want to use it also has this link: https://rathena.org/board/topic/82370-costume-npc-and-costumeitem/page/4/
 
So the question is: How do I apply the .diff files to the src of my emulator patch? is it manually have program for this?
If it is manually what is the step-by-step used to adjust it to my src files?

I thank you for your help and assistance