Go to main.js and copy and paste it (the whole thing) then run it in the browser js console (Right click then go to inspect element then press console tab) on a website or go to about:blank for a blank page the most known website it has support on is: Youtube
If you have already ran it tho want to change it to a different site now then use this and change the URL to what you want (main2.js)
You can change the URL to any existing site not just sm64js. (just so you know)