What you need to do is:
Undo the bolt that holds the roll bar to the chassis and remove it and the 2 washers. Now place the ringlet that's in the strap on top of the roll bar and put the bolt back through the washers, the ringlet and the the roll bar.
Do up bolt (toque to 20 Nm says manual) - jobs a goodun!!
On the build manual I'm looking, the bolt can be seen in the picture in Section 16 (Options) Page 5, Figure 5, item 2
Oxted used my 7 for the pictures and instruction write up, so I hope it's not changed from what Ive just told you.
I'm at work tomorrow but you can contact me via my profile if you need more info - I'm about 15/20 mins from Brands so you could always pop over (even thou I won't be there) for a gander, as the 7 lives on the drive.
Hope that helps
Mike