Below you will find the steps needed to change the DNS Nameservers for domains registered with 1&1.
1) Login to your 1&1 control panel.
2) Click Domains from within the Domains & Webspace panel
3) Check the checkbox next to the domain you wish to modify, then click Show DNS Settings from within the DNS menu.
4) Click the Edit button located next to the Name Server Settings section.
5) Under the Domain Data section, select DNS.
6) Found within the Basic DNS Setting section, select My name server from the dropdown.
7) Select My secondary name server from the Secondary name server dropdown.
8) Enter your primary name server in the primary name server field. Then enter your secondary name server in the secondary name server field.
9) Click OK