Confirmations refer to the process by which you verify that a recipient wants to receive email from you. This is often called a double-opt-in because recipients must affirmatively express interest before they received any additional email. The process with Symphonie is to first create a Document of type Confirmation which will be sent to the recipient to ask them to click a link to express their agreement to receive additional emails. You get to design the content that is sent, in the language you choose. Within the content must be the mail-merge tag that generates the link back to Symphonie for the recipient to click to show their agreement.
To mark a recipient as being in the double-opt-in status, simply use this API to send them the confirmation document you created. Symphonie will deliver the email and mark the recipient record in a status that will prevent any other emails from being sent to the recipient until they confirm their interest. You can queue emails to an unconfirmed recipient, but Symphonie will filter it out before sending.