Point the "DOT" on the filter ring towards the light source (Sun). If you're using a TTL meter, just use whatever exposure your camera suggest. If its an external meter, use exposure compensation between +1.5 to +2 depending on the intensity of the polarisation.
There is two filter rings on the polariser filter. One which screw on to your lens and the other which you can rotate. Just compose your shot and slowly rotate the outer ring until you get the effect that you want.
Polarisation effect the would depends on the angle between the sun and your shooting direction. For max. effect, it is usually 90 degrees.
You can try this out by pointing your lens towards the sky and rotate the filter. You will notice that for certain angles between the lens and the sun the polariser has very little effect.
If you meter through your lens, no compensation is needed. The white dot is only for reference only.