please ignore the rude posts.
You rent a car, you go out and buy a small inexpensive table top (barbeque) grill (gas or charcoal) , along with hotdogs, hamburgers, sausages, buns (bread for each) and or chicken wings. and of course beer.
You show up early (3 to 4 hours prior) to the game, (maybe ask the attendant where the tailgating section is) park the car light the fire, cook your food and drink your beer.
Yell GO Bills and enjoy.
they will not let you bring beer into the stadium itself, so leave it in your car.
check the Bills website for details on what you are allowed to carry into the stadium.