Casting bullets from a pot placed on the coals of a fire is an exercise in frustration, low productivity and scorched knuckles even if you wear the obligatory gloves.
Use a propane burner or Coleman. Do NOT use an aluminum pot to hold the lead, you need cast iron. Aluminum pots, when filled with lead and placed over heat ample enough to melt lead, get weak bottoms. The weight of the lead will suddenly plunge through the weak aluminum bottom and may seriously injure you.
The American Rifleman has had numerous warnings about melting lead in aluminum pots for years. Cast iron is the way to go.
You will need to use dead-soft, nearly pure lead. Wheelweights are made of an alloy that is too hard. I've fired wheelweight alloy balls in my own cap and balls. The lead ball is hard, making it difficult to ram down, and accuracy is lousy. Hard bullets and black powder are a poor combination.
Soft, nearly pure lead is often difficult to find today.
You really want to get into casting? You can buy .454 inch balls much cheaper than an investment in a pot, burner, ladle and so on.
But if you have the bullet mould, give it a try. Wear long, thick leather gloves. Never let any kind of water near your molten lead. Water dropped onto molten lead can cause the molten metal to explode upward, giving you bad burns.
Cast outdoors, in good ventilation. Handle all lead while wearing latex gloves, or the aforementioned gloves. Lead poisoning is possible, but it is usually contracted by eating or drinking with lead on your fingers.
Lee moulds come with very good instructions. Read them. Smoke the mould cavities with an old candle stub, to put down a layer of soot on the cavity. This will help the lead fill out the cavity.
Bullet casting is tedious. If you have a bunch of soft, pure lead then it's worth it. But it takes time too.
I've been casting bullets since about 1971, for modern and black powder guns. Bullet casting can be fun and fascinating, but weigh the cost of equipment and time against just buying a few boxes of balls.