If it's a 2007, it's under the seat. Remove the two allen screws one either side of the underside of the seat and the one bolt behind the passenger pillow. Lift off. Now move the electronics out of the way and remove the one phillips screw holding the battery cover on. There you go.
I had a 1997 Honda Shadow Spirit VT1100C and it's battery was behind the large chrome cover on the left side of the bike just below the saddle. If this doesn't answer your question, try re-listing it and include the engine size as Honda's are very different one engine size to another, i.e. Shadow 600 (VLX) is completely different from Shadow Spirit 1100 (VT1100)
Under the seat
I have a 2006 Honda Shadow 750 and it's battery is under the seat. You have to take the seat off of course to get to it. It is very small.