Basics
Wait Until Page Renders
Minimally you only want jQuery to start once the page has completely finished rendering. Do that by starting with this,
$(document).ready(function() { // all of your code goes here });
Referencing Elements
To reference elements see the following,
$("#myID") // find first matching ID element $(".myClass") // find first matching class $("p");
Start Doing Stuff
Assuming we have a CSS class called funky that in this example makes the background yellow.
.funky { background-color: yellow; }
Add Class to Element
$("#myID").addClass("funky");
References
Good Intro - http://www.catswhocode.com/blog/learning-jquery-the-basics