The easiest way is to go purchase a tin of Stagg chilli which is very delicious and come in a few varieties.
My way of cooking chilli (which is pretty easy) - dry fry 1lb minced steak/minced beef and add 1 chopped onion and continue frying for 2 mins until onion soft, mince brown. Add 1 tin chopped tomatos, 1 tin kidney beans (drained) handful of mushrooms (optional) 1 chopped red/green pepper (optional) 1 beef stock cube, large pinch of salt, and chilli powder - 0.5 teaspoon of red chilli powder for mild, about 0.75 for medium, 1-2 teaspoons for hot to flipping hot. Bring to boil, mix well, simmer for at least half an hour (stirring occasionally - must be half an hour allow flavours into the meat) In the last 2 mins of cooking add a large dollop of tomato puree to thicken. serve with a big bag of nacho chips and a bucket of lager. Alternatively you can use fresh red or green chillis for a better taste, but it's all experimental as to how hot you'll get it (which is usually part of the fun!)