To start off you may want to do little things. Try drinking water instead of anything else. (if you need to, drink diet soda and real fruit juices) use mustard instead of mayo, eat soy chips instead of real chips, whole grains in place of white grains, etc.
When you're done doing that, start cutting down your meals a little. You said you eat way too much and excercise too little, so you know what your problem is. You don't need to exercise to lose weight, but if you want to get healthier, then you should. But decreasing your caloric intake will ultimately make you lose weight.
When I lost weight I didn't workout, I just cut all my meals. I didn't eat breakfast (but you should, it helps, I just hate breakfast), I ate a small lunch, a healthy snack after school, and then a normal dinner.
When chosing the foods you do eat, try to pick things that are high in protein and fiber, moderate in carbs, and low in fat. Stay away from saturated fat and trans fat, but you can have polyunsaturated and monounsaturated fats moderately.
If you need something sweet, eat fruit. And if you need your chocolate and something of the sort, try treating yourself with bite size candy pieces, but only limit yourself to one or two a day.
This is all my opinion and what worked for me. If you have any questions, ask.
