r/place canvas downloader

userscript.user.js

// ==UserScript==
// @name         r/place canvas downloader
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  download the r/place canvas
// @author       adryzz
// @match        https://hot-potato.reddit.com/embed*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=reddit.com
// @grant        none
// ==/UserScript==

if (window.top !== window.self) {
    window.addEventListener('load', () => {
        //wait for everything to load
        setTimeout(() => {
            //get the help button
            document.getElementsByTagName("mona-lisa-embed")[0].shadowRoot.children[0].children[0].children[3].children[1].shadowRoot.children[0].shadowRoot.children[0].onclick = function(){
            
            //get the canvas
            var canvas = document.getElementsByTagName("mona-lisa-embed")[0].shadowRoot.children[0].getElementsByTagName("mona-lisa-canvas")[0].shadowRoot.children[0].children[0];
            var dataURL = canvas.toDataURL("image/png");
            var a = document.createElement('a');
            a.href = dataURL;
            a.download = "place.png";
            document.body.appendChild(a);
            a.click();
        }}, 10000);
    }, false);
}

how i can run this script?