Can someone explain me how i can add my home made alpha map for 1 texture as a terrain splat map please? Step by step guide would be great.
Also, lets say i edited some of the terrain shaders, how would i use them on the terrain itself?
There is no way of adding a particular shader to the terrain, as the terrain has no renderer component, and no material assigned in the traditional way. That is the main reason you see a lot of people coming up with various ways of getting extra stuff in.
Unity has the smart concept though if it finds a .shader file in the project with the same name as one of the inbuild pre-compiled shaders, it will use that instead. So what you need to do, is downloading the source code for the inbuild shaders (you can find them as a sticky thread in the shader forum), and then change whatever you want in whatever shader you need. You then save the modified shader into the project structure, and re-open Unity. That’s it. From now on your modified shader is the one being used.
But getting terrain shaders to actually work with out bugs and stuff, is a long an tedious learning experience. I hope you’re up for the task 
I don’t have time for a step by step guide now, but maybe others do…
So, forexample i change a small part of only 1 of the many terrain shaders and put it in the root or in any folder of my assets with the same exact name and thats it? I dont have to do anything else?
if thats the case, thats simple 
What about the splat map thing?