Drink lots of water and no seconds from a meal and no sitting around doing nothing after said meal.

Eat smaller portions throughout the day rather than large meals. Large meals, I'm no expert but this is what I've read, are harder on the body to digest while eating small portions throughout the day is easier on the body. Also, eating throughout the day doesn't mean Oreos, chips, or other fattening shit I mean like nuts, dried or fresh fruits, and etc.

metalman has given excellent advice. To begin with, fix your schedule. For example if you have a horrible schedule. Press the red, "End" button right now. Wake up early. Something in betweem 4-7 am. Have a healthy wholesome breakfast, for eg. oatmeal with fruits and cream. Not 7 bowls. 1 & a half would do. Excercise for an hour and a half (basically begin with half an hour the first day and then timely increase that to a maximum two hour time span of work out in the morning.)
Then for lunch and dinner, mainly have protein, for example grilled fish or chicken or lentils or beans. I cannot here give you an exact diet plan, but this might give you a gist of it. But remember the amount of your meals should be in descending order. For example your breakfast should be more than your lunch and your lunch should be more than your dinner. Also ensure that you incorporate cheat meal days, however on those days your excerise heavily enough to match the calories you take in. Good luck!

So lets say for example I'm supposed to eat 1500 calories. Would I have to exercise to get rid of those 1500 or is that how many I'm supposed to have at the end of the day ?

Yes. You must exercise every day. And no that's not the amount of calories that you're meant to have at the end of the day. Gogogo. Good luck. Here, if something I explained doesn't make sense.