I take it that you have got a normal distributor. If so you need to firstly remove the cap, turn the engine over and watch for the rotation ie clockwise or anti. Then you will need to set your engine so that number 1 cylinder is at TDC (top dead centre) on its firing stroke. When this is set if you now look at the distributor rotor arm in relation to the cap, the lead coming from that segment aligned to position of the rotor arm will be number 1 cylinder. Given that your distributor rotates say anti clockwise you can then work out that the next lead would be number 3 cylinder and then 4 and 2. We are not sure what firing order you have but it would be either 1342 or 1243