You can only "point" a domain to 1&1 name servers if the domain is currently registered with another company. Pointing a domain to the 1&1 name servers is an alternative to the Transfer of a Domain to 1&1.
You will receive a confirmation message upon the completion of the ordering process. You will also receive an e-mail shortly with additional information and steps to follow to complete the process with your current registrar. This process may take up to 48 hours to complete.