You should always pre-season your wok to be on the safe side. Cast iron works need special care when cleaning afterwards so that you do not end up removing the seasoning.
To begin with, you need to clean your wok properly with sponge and soap so that all the dust and germs are removed. Use hot, soapy water to scrub the inside and the outside of the wok. In order to season your wok, you will have to use an oil with a high heating point because the food you cook will be very hot. The oil should be refined and have a neural flavor like peanut oil or sunflower oil. You can either season your wok with the help of the stove top or the oven.
Oven: To begin with, you will have to preheat the oven to 450 F. Use a paper oil to sponge on a thin layer of oil over the entire wok. You have to line a sheet pan with aluminum foil and keep it on the bottom rack if the oven. After placing the oiled wok on the top rack, you will have to bake for 20 minutes. Rinse it well afterwards to complete the process.
Stove: You have to preheat the oven over high heat in order to open up the pores in the metal.
You might see smoke but there is no reason to be alarmed. Make sure that you heat it from all sides. Now, coat the wok with an oil that has a high smoking point as smoothly as possible. Heat up the wok over medium heat again to complete the seasoning. The wok will have a matte finish by the end of the process.