Okay, oppose, what type of beef are you sauteeing? If it's ground beef, it's quite easy.
Put the ground beef and onions (chopped probably) into a large skillet. Turn the heat up to medium or so and stir the meat and onions around as the beef begins to cook. The beef will start to brown and the onions will begin to turn a bit translucent. Keep stirring until the beef is no longer pink and is browned to your liking. Turn off the heat and drain the fat/grease from the pan and continue preparing the recipe as it directs.
This is the short lesson for ground beef.
"As a girl I had zero interest in the stove." - Julia Child
This is real inspiration. Look what Julia became!