How can I join my workstation (my personal machine so not in a network) to the domain (Windows Server 2008 R2 is the host).
First thing is you talk to an admin and let them know that you want to do this. They may have a "no personal machines on the network" policy and you risk violating it, which could land you in a heap of bother.
Assuming that you've a version of Windows that can join a domain, your domain may be configured to use a user account dedicated to joining machines (this is an MS recommendation). If so you'll need the user name and password of this account in order to join, which I guess your admin won't idly give you.
What's the operating system?
Non-business versions of Windows explicitly forbid joining a domain. Otherwise, it's just advanced properties of My Computer, and it's on the Computer Name tab.