How to use Javascript on a page

Hello everybody,

The Javascript that you see at the top of this page is from an old html site that I would like to use on my new WordPress site. I have searched for other dropdown menu’s but did not find anything that works the same way as the Javascript. I also tried to just paste the code but that leads to nothing. I do understand, however, that Javascript can be used within WordPress. Would anybody be so kind to explain to me how I can make this script work on my site? It would just be on one single page. Here is the code:

[Please use a pastebin for posting that much code –
http://codex.ww.wp.xz.cn/Forum_Welcome#Posting_Code%5D

Thanks!
Rutger