You'll need to remove the top-box mounting frame (4 bolts), then the tail light plastic assembly (2 bolts - one either side). The one on the off-side (if you are doing this on a wee) is a pig because access is blocked by the exhaust. I find the nest way is to use a bit with an adjustable spanner attached to get inside the area between the tail light assembly and the exhaust. With some manipulation the tail light assembly will come loose. Just don't let it go because it has the wiring loom for the rear lights \ indicators plus the seat release cable mechanism.
I think this is how you get to it, had to get to a switched feed a couple of weeks ago in that area so had the assembly off for that. Caveat: I've never actually had to remove the indicator stalk so I may be talking utter rubbish. If I am then someone will be along shortly to correct. If it's anything like the front then it's just a case of undoing the nut and the connector and sliding it out of the tail light assembly.
