hps help

hi im new to growing iv got a cupboard about 3ft x2x2 i bought a 70w hps bulb it says requires a external ignitor,could some one tell me what that is and if it is nescesery,i have a fitting that will house the bulb but do not have a ballaset,pls if anyone could help it would be great thanks

HID bulbs require a ballast to ignite. You can't use just any socket and light it up.