Use the drop-down menu to switch between different scripts (u can also double click various parts of the code w/in any of these snippets to learn more about each piece of the code.). Click the "copy+paste" button to copy the current script to ur clipboard && then open the Developer Console (Fn + F12) && paste ( + v) && enter the code.

For a more detailed explanation refer to my notes on the browser's dev tools, specifically the Console tab if u're unfamiliar w/these. i've also got notes on how to package any of the following snippets (or variations thereof) as browser addon-ons for quicker re-use && sharing w/others using the addon-on editor.