You want an oil with a high smoking point ie; grapeseed, wipe it all over the lid and base (inside that is), if you have a bbq use it instead of the oven (if you only have hot plates take them off and rest the lid or base on the flame), crank the heat up and turn so it gets even heat across the entire section your seasoning, wait till it smokes and starts going blue black, remove and wipe down with paper towel till clean-ish, repeat until it has a semi non-stick surface.
It usually takes 3 goes, I like to do the last one with some ghee.
Their not the best for roasting I prefer cast for that but they are excellent for breads and fry pans. If you do use it for roasting don't put it directly on a fire or coals, you'll burn the crap out of whatever's on the bottom. Some might say use a trivet?? I haven't had much luck with it??? ha it rhymes
It's all about experimenting, you'll get the hang of it.