ABS sensor's normally self reset, sometimes you need to run the vehicle above 10-15mph.
If the light has stayed on either you need a diagnostics kit (scanner) to reset it or it's not the sensor.
How did you identify the faulty sensor & have you checked the ring that the sensor reads
if it's a toothed ring then corrosion under the causes them to crack (check it very very carefully) which can give a ABS fault, if it's a magnetic ring they can loose their magnetism (usually after someone interferes with it or the wheel bearing).