Welcome to 3FC =)
It can really seem overwhelming starting out.
The good news is that it can be cut up into manageable bits.
Activity: You do not have to force yourself to do anything that you absolutely hate doing. If you don't like team sports, then there's no one holding a gun to your head to force you to do them. There are plenty of ways to add in activity and exercise to your day. Little things, such as parking far from buildings and taking a stroll before going inside. Taking the stairs instead of elevators wherever you go. Planning a daily walk around your neighborhood, etc. Or getting a cheap exercise dvd and starting out doing 15 minutes a day. Even turning on music and dancing around in your room is activity.
Food: How about calorie counting? At least to start. It's cheap. It's easy. And it's flexible. Check out the Calorie Counting section under Diet Central to see how it works. You
never have to starve yourself to lose weight no matter what you chose to do.
Your parents might not be healthy eaters, but that doesn't mean you have to follow in their footsteps. Offer to help by going grocery shopping with them. Or offer to cook a meal or two a week to lend a hand.
Remember that even if you don't cook the meal, you are still in control of your portions. Eat half of what you used to, and add in vegetables to bulk it up.
Drink more water. Eat more fruits and vegetables.
These things will add up over time. And in general they're just healthy habits to have for life.
Over time you'll figure more out about what you can do, and what fits your life and schedule. In the meantime these were just a few suggestions of where to start.
Take a deep breath. You don't have to be perfect. (No one is) You just have to keep aiming to make healthier choices to start.