CouchPotato xREL

CouchPotato-xREL.user.js

// ==UserScript==
// @name         CouchPotato xREL
// @author       jayme-github
// @namespace    https://github.com/jayme-github/
// @downloadURL  https://gist.githubusercontent.com/jayme-github/becb38ac3577574df74e/raw/CouchPotato-xREL.user.js
// @version      0.1
// @description  add xREL search link to wanted page
// @match        http://192.168.2.240:8083*
// @match        http://127.0.0.1:8083*
// @require      http://code.jquery.com/jquery-latest.min.js
// @copyright    2015+, jayme-github
// @grant        GM_xmlhttpRequest
// ==/UserScript==

function add_xRel(event) {
    console.log('xRel: ' + event.data.source);
    setTimeout(function() {
        $(".imdb.action.icon2").each(function() {
            if ( !$(this).siblings('.xrel').length ) {
                var imdbaction = $(this);
                urlsplit = imdbaction.attr('href').split('/');
                imdbid = urlsplit[urlsplit.length - 2];
                //console.log(imdbid);
                var xrel = GM_xmlhttpRequest({
                    method: "GET",
                    url: "http://www.xrel.to/search-instant.html?_ac=11540&q=" + imdbid,
                    onload: function(response) {
                        xrelurl = $(response.responseText).find(".big").attr('href');     
                        $('<a title="xREL" href="'+xrelurl+'" target="_blank" class="xrel">xREL</a>').insertBefore($(imdbaction));
                    }
                });
            }
        });
    }, 1000);
}

$(document).ready(function() {
    $('.tab_home').click({source: "home"}, add_xRel);
    $('.tab_wanted').click({source: "wanted"}, add_xRel);
    $('.tab_manage').click({source: "manage"}, add_xRel);
    add_xRel({data : {source: "main"}})
});

Hey.
Can you tell me something about this script?

Where can I put that into, to enable it CP?
What does it do?

Jus searching imdb within xrel? What is the output?

THX a lot