That looks similar to the one i have. You need to chop off part of the undertail. It's kinda hard to do without instructions. You also need to cut out where the luggage hooks are. You'll obviously have to take off the old tail light. You'll have to take off your rear sets too because that is where one set of the screws are. Just start by taking your tail section off, the tail light out, and look around and see what you have going on. Once you chop the fender there isn't much you can do to reverse it so be sure you want to do it. If you bought this off ebay you should ask the guy you got it from if he has instructions. Hope this helps.
The guy I bought my bike from gave me an extra set of bodywork with it that included this undertail. There are little rectangles cut into it to allow the hooks to poke through, which I rather not have but oh well.
Anyways, ill just pull it all apart and take pics and post up if I run into trouble.