When you install and activate the plugin it will search in the database for an API key to enable the extra features, if the key is not there then a big blue button will appear at the top of the administration panel displaying the email address of the main user account and the domain name that will be used to generate a new key.
If you click this button the plugin will communicate with Sucuri to generate the key using that email and that domain, if they are valid data then the key will be stored in the database of your site and displayed in the settings page.
If you are having problems generating the key by yourself then contact us at info@sucuri.net and one of my co-workers in the support team will generate it for you, remember to send the email address and domain that you want to use to associate the key.
