Fit together the new bar end. Note: the conical metal part on the left of the pictures is the threaded one and is on the opposite way around to the way it came in the pack.
Hand tighten the conical bolt, until it is snug against the funny metal spacer thingy (the technical term!). Insert the whole thing into the end of the bar and tighten with an allen key. Try to leave a small (1mm) gap between the bar end and the end of the grip, on the throttle side bar. This lets the throttle turn freely.
Then attach the Rizoma mirror stalk. You can hang them under the bar but this didn't look "right" to me so I did them this way. I used the white spacer that came with the mirror. It went on the clutch side easily but was a tight fit on the throttle side. I think it would have fitted without the spacer but had to be really tightened and I was worried that the circle of the clamp was quite deformed by the time I got it to grip, so I used the spacer.
Finally screw on the mirror, with the supplied screw (it is hidden behind the first layer of foam in the box, if you can't find it!).