How to install PHP extension locally on WAMP?

I've never done this, so I'm looking for detailed guidance. I'm trying to use the Evernote API to create a PHP page. I've downloaded their SDK and it says I need to install OAuth extension for PHP. I have WAMPSERVER installed on my local machine (Windows 7). I've tried reading the manual but I can't even figure out what to download :S Is this a fairly straightforward process?

http://php.net/manual/en/book.oauth.php