Not much to say just feed the float onto your line the set up your feeder/bomb on a running rig. Cast out the tighten till the float is cocked and just showing. They are meant for deep water where traditional float ledgering is not possible. Its fun to watch the float dissapear but i prefer to quivertip you get better conection on a bite at distance.
Put a stop shot 3ft above the feeder or bomb to stop it going right down.
It becomes difficult in a good wind or if theres a tow on the water. Like Bryan says it can sometimes be easier to use a quiver then.
Remember you are striking through 90 degs on a line from rod tip thru the float and down to the fish so you need a good strike to connect in deep water.
I have a few, but rarely if ever use them. Their main problem is that when you strike you create a lot of surface and sub-surface disturbance and it can scare off fickle fish like bream.
As Bryan says, the quiver is much better and even then keep the strike low (in line with the line, if that makes sense) so it pulls straight through the water to the feeder or bomb.
i use them regular. the no1 polaris for carp+cats hair rig with hallibut pellets. or worm on the hook. the advantage is that you allways have something to aim your loose feed at. i dont bother putting a shot above the lead as if your line is tight the float wont slide down anyway. i also use them for fishing margin swims that i have prebaited as you havent got to mess about keep changing depth.
They are good for fishing just over the marginal shelf of gravel pits for Tench where conventional feeder fishing would be hindered by the line cutting over the edge.
as regards what rod to use it really depends on the size of fish you are after. i use a carp rod when after carp+cats or a avon rod when after tench breem puddle carp etc. the big polaris floats have no trouble with fishing 12 pound line.