How do I implement hook_views_pre_render()? I need to alter the result of a view. I read I can use hook_views_pre_render(), but in a custom module. I don't have any custom module implemented and I would like to know where and how should I put the code in my project.
You need to read and understand the Module developer's guide first, then it's as simple as adding the following to your .module file:

function MYMODULE_views_pre_render(&amp;$view) {
  // Do stuff with the $view object.
}