How can I get in shape?

I'm 15 and 5'7. I am not overweight at all but I'm starting to get a bit of a muffin top. I need some excercises that can help me get into better shape. Like maybe some simple ones, and then some that can help get abs maybe. I want to start of light because I'm getting very lazy lol. I eat quite healthy except for the past week we've had guests so I've been a bit slack. My parents won't let me go out for a walk by myself. But we have a tredmill, a bike thing, another stand up bike thing and a punching bag in the garage. I just can't get motivated to do any of this stuff. Please I'll take any advice! I want to start being a bit strict on myself so I don't become a couch potato. Thank you!