What Voice said.
There are two WordPresses. www.ads-software.com is this one, where you get stuff for your website.
WordPress.com is a free version for people who don’t have their own domains like your .com address.
WordPress.com is different than the one you’re using now.
You must sign up there. There’s a big green button there that says “Sign Up Now” Click it and enter all the information it asks for. The blog you are registering for there has NOTHING to do with the one you are trying to set-up on your website except for the fact that that’s where they will give you an API key.
It doesn’t have to be the same name as your current site, you can use a different password if you like, and you never have to use it if you don’t want to. Again, after you sign up there, click “Profile” in the upper right corner and you will find your key there.