Male, 21, 5'11'', 145lb, with belly fat. Any advice?

Hello, fellow redditors! I found this sub-reddit just a week ago and your advice has been of great help for me. However, I still have a question. Here's my situation:

I want to start gaining weight and working out soon but I am concerned about my belly fat. My lifestyle is very sedentary and I also used to consume lots of soda, iced tea, cookies, pastries and chips (stopped about three months ago).

I have noticed that my abdomen returns to a "normal" state if I eat smaller amounts of food, so I think this involves more than just fat. My dad suggested as a joke that my stomach pushes out when it gets full and my weak muscles cannot hold it in place, creating that effect. Is that even possible?

Anyways, my question is: how can I get rid of belly fat while trying to gain weight?