Active Directory is pretty intense for someone asking questions like you have. You need to be familiar with DNS and probably DHCP also. I'm not sure how you got assigned to this, but it would be best for a professional to do this as you helped and learned along the way.
I took several courses in Microsoft server and domain systems and I still don't have a full grasp on how it all works. If you don't already know a lot of this going in, you are going to face a really steep learning curve.