Wash then with a quality, mild, car wash solution, mixed correctly.
Once they are dry, take any quality cleaner polish and clean/polish them with it.
Then apply any quality sealant to the wheels, allowing it to dry/cure completely then wipe off.
In the future, if the wheels are not crude coated with brake dust, just spend a little time and clean them with the car wash, agitating them with a mitt or soft bristle brush.
Grumpy