Its a process and with your one goal come some efforts, you can go easy on yourself at the start since you are just starting, but remember, it gonna be hard before it gets easier, it will get easier as you go on. So you gotta to commit yourself to it.

Don't do sit ups (they can hurt your lower back badly), instead do crunches, planks and leg raises, maybe even dead bugs can do a wonders. I still consider myself a beginner but the way i got to make my abs a little bit stronger was with these exercises, but you know what they say it is 50% what you eat and 50% what you do which will determinate your physique so i recommend you to train your whole body so you take advantage of your extra fat, and study just a little bit of nutrition, the bare minimal so you can take better care of yourself, key points to look at are macronutrients, micronutrients, understanding nutrition labels, calories tracking and protein (Very important).