How do I get my XM radio to work?

I got a new XM satellite radio for my birthday (today, yey 28!). Anyway, I'm at work and I set the whole thing up. Problem is I cannot get a signal in my office. I have the little satellite thingy and I've tried moving it all around my office, but I cannot get a signal. Is there anything I can do to get it to work? And yes, I tested it at home and it works fine there. My office has 4 walls and I am not near a window, which may be the problem.