All good advice above.

I will add that you might like to look at your portion sizes. That's a good way to begin before looking into nutrition and the types of food you are eating. Many people don't realize that the amount they are eating is way above what a portion should be.
Portions, in my opinion, are realllly smallllllll.
Add some exercise to your routine and you are on your way. At that point you could look into calories, specific foods AND drinks. Lots of types of beverages contain a lot of calories and/or sugar so that's a great place to start looking for what's putting the weight on.
Good luck!