A popup will appear where you can enter the details to link your account.
Account name: This is for you to easily distinguish between accounts if you have multiple Mandrill accounts.
Service: At this time, you'll only be able to link Mandrill as your mail sending service.
Mandrill API key: You can find this in your Mandrill account.
From email address: Enter the email address that recipients will see when they are sent an email. This must match the domain registered in your Mandrill account.
From name: This will be the name that recipients see when they are sent an email. This can be the name of your company or organisation.