Idk what foods to eat so I haven’t been eating v much. Need advice!

So I’m trying to lose back and arm fat, and gain muscle in my butt. I’m not sure what I should be eating though??

I’ve always thought you should eat very little and only healthy stuff like fruits and veggies and little meat but recently I heard it’s opposite. I’ve eaten junk food my entire life so I really dunno what do eat lately.

Could you guys give me examples of what I should eat in a day. Like if you say “protein” then what foods exactly ? And what proportions?

Currently what I eat in a regular day is:

Morning- cocoa / hot chocolate

Lunch time I’ll have half a ham n cheese sandwich w chips. And glass of chocolate milk

Snacks I’ll have oranges, cookies, sometimes cereal but that’s sorta a meal.

Dinner- stoffers (frozen foods😬) , or whatever my mom/ dad makes which is usually chicken and rice w either milk or choc milk again.

That’s usually what it is. And yeah I have a chocolate milk problem. I am trying to cut it down to 1-2 glasses a day instead of rn it being close to four