boiler warning light is on- how do i reset it?

last night i had a radiator connected to existing pipes. when i got up today there was no hot water. i checked the boiler and the warning light was on. i noticed the pressure bar was low (0) - so i raised this to just over 1 but the light is still flashing? there is no blue light to indicate the ignition is on but i am not sure how to do this? please help its cold and i have no hot water. i have now turned the power off to the boiler.