ftp user
Specifies a user to the remote computer. Windows commands reference
On Windows
Windows
user <username> [<password>] [<account>]user User1 Password1
<username>Specifies a user name with which to log on to the remote computer.[<password>]Specifies the password for username. If a password is not specified but is required, the ftp command prompts for the password.[<account>]Specifies an account with which to log on to the remote computer. If an account isn't specified but is required, the ftp command prompts for the account.