Hi Stephen,
I'm sorry if my video wasn't clear on how to get an API key and set that up. To get that you need to signup for a free account at WordPress.COM. Yes, I know it's weird that you have to go through the .COM version of WordPress, if you're using the .ORG version on your own hosting; but that's the way API process is setup.
Once you have signed up for a free account at WordPress.com, you can find your API key within your User Profile, which you will access here:
http://genesisblogging.com/images/wp-apikey-1.jpg
Then once you are on your User Profile page, you will see your API key at the top of the page, like this (obviously, I've blotted mine out, but where you see the black line, is where your API key would be located):
http://genesisblogging.com/images/wp-apikey-2.jpg
Just copy that key, then in your WordPress installation for your domain, click Plugins > Akismet Configuration > then paste in your key. Click 'Update Options' and that's it.
http://genesisblogging.com/images/wp-apikey-3.jpg
Hope this helps you; if not - let me know. :)
Edited to say: if you installed your WordPress through your own web host, such as through Fantastico, then you have the .ORG version. The .ORG version is the only one that works with your own domain and your own hosting.