Here are some basic tips that I have used since the start of my program, I am giving you this answer based on the fact that you have given absolutely no information what so ever.
1. Make a diary of what you eat each day
2. Eat healthy
3. If you eat Breakfast, Lunch & Dinner. Start cutting it down to 6 meals a day and smaller meals.
4. Exercise and plenty of it, to lose weight you have to burn calories (HITT is a great way to lose weight)
5. Drink plenty of water
6. Get plenty of sleep
Just remember you get out what you put in, and diet is a large part of the whole process.