First you need to open the page with a HTML editor such as dream weaver or front page or even note pad , notice that if you using any other page making (ASP, PHP , etc.) languages it doesn't matter. Just open it and access to source file.
When you Open it, there are some codes in HTML called tags:
you have to find something called "BODY"
In HTML code it's like
When you find it just skip a line and copy and paste after body tag the codes which we offered you in this website
Anyways if you couldn't find that just paste the codes in the end of the source file.