Your license.
An account is an email and nothing else. Type it, and the license comes back — shown here the first time, and mailed. Paste it in Vigia under Add Slots; that computer is the account from then on, and the server slots you buy are issued to it.
Check your mail.
This address already has an account. A six-digit code is on its way to — type it below and the license comes back here and there, with every slot key bought for it.