I bought the flash but don't have the manual. Does anyone know how to use the flash?

It's TTL metering, but the slider to set the ISO sensitivity has two bars to indicate the effective distance, one with stripes and one in blue. Is the blue meant to indicate the max distance for High Power and the stripes for Low Power?

Also, it has an auxiliary AF illuminator, can my EOS 500 activate it in low light? If so, how?

Any help would be appreciated!