A Form of Authorization (FOA) email is sent to you from your current registrar. You must respond to this email to authorize the domain transfer. This helps prevent someone from initiating a transfer without your permission and hijacking your domain name.
The email is sent to the administrative email address associated with your domain name. If you are not sure whether you have access to this email address, please contact your current domain provider. If necessary, ask them to update your email address and waive the 60-day Change of Registrant lock. Although ICANN allows providers to waive the 60-day lock, this is not required.