the rubber sits on the bolt, which should be threaded, probably not all the way up, some come with nuts, some don't, if not, get some locking nuts the right size from ur diy store (or ur dads shed, like me!)
as regards fitting, like 16v jon said, put it on axle stands at the front, take off the wheel, jack up the wishbone you're working on, but not so far it starts to lift it off the stands, get a long bar, lever onto the top of the bolt head, get someone to hold it or chock it with something (don't use the 1st thing that comes to hand, a plant pot in my case, disaster!) apply a bit of thick grease to the shaft, but not the thread, then thread the nut on, tighten until u see a mm or 2 of the bolt. take the bar out, release the jack, repeat on the other side. replace the wheels, take it off the stands, job done.
