Hi Mr Faust,
First off, there is a ton of more experienced people on this forum. I consider myself a noob as well. Their advice is probably much better than mine, but I have dealt with this issue so I am going to go ahead and post.
What is your role in the company? Are you part of the IT dept. or just an employee who shares an interest in security?
A lot of people here are going to shoot you down and rightfully so. BackTrack should not be used on a live network, even your own company, without explicit written permission from whoever manages that part of the company. You could be setting yourself up for a legal issue if you try to do something you don't have permission to. You also might want to consider who you want to "hack" into. If this rogue AP belongs to a branch manager you might be barking up the wrong tree by "demonstrating" how insecure this is. Another point is it sounds like you don't know what you are doing (respectively speaking to using BackTrack), you could end up making things worse for the network.
If you are in a position of being able to do what you were saying you might want to see if your company will invest in taking some of the training from Online Security Training from the Creators of BackTrack The pentesting101 course with BackTrack is an amazing course as well as the Wireless class. I have taken both and highly recommend them.
As for the original issue, this can be done many ways. If you do work in the IT dept. for your company you ought to have some switch level/router level access. You can start by sniffing the traffic with wireshark or airodump-ng, then block the port (either by MAC address or turning off the port) on the switch or creating ACL on the router. This is assuming someone just purchased a wireless AP for example and plugged it into a port picking up an IP on your network. A lot more information is needed for how your network is managed, to proceed.
It sounds like you are really want to learn BackTrack, you ought to consider the classes offered by the remote-exploit team I posted above. Hope this helps