Before you set up Akismet on your WordPress blog, you need an Akismet API key. To get an Akismet API key, you need to have a free WordPress.com account. So head on over to the Akismet website and get an Akismet API key. If you already have a WordPress.com account you can sign on using your existing account or you can create a free account.
Once you sign in, you will be presented with an Akismet payment plan. You can select the payment plan that suits you. If you are using this on your personal blog or for non-commercial purposes, and you don’t want to pay anything you can select the donation plan and pull the “amount to donate” slider to zero. Akismet is an amazing service and it will save you a lot of time so if you are using this for a commercial site, you should definitely consider paying for it.