This may be obvious, but you also must have a domain account with rights to add a computer to the domain. With the requirements out of the way, let's start with some preparatory, one-time work you'll ...

Organizations with an AD infrastructure in place that wish to provision Linux computers can bind those devices to their existing domain.

The default Windows 2000 domain policy already allows users to add computers to the domain. If you want to specify a specific user add it to the default domain policy in security settings->Local ...