How should my eating habits be? (Slim guy trying to strengthen ABS)?

So, I'm 23, Slim build (not skinny but not muscular either, a pic of my body is attached) I used to workout moderately but I haven't in maybe half a year, and i want to get back to it, but I'm really confused on one thing: My main goal is to strengthen my ABS and make them popping and toned, but at the same, i don't wanna stay in a skinny build; I'd love to get more buff and muscular, but I'm facing a dilemma For ABS strengthening and a toned stomach, i need to eat very healthy and mainly consume protein But to get more muscular in other areas (biceps, chest etc.) I need to eat a lot more and consume a lot more calories than i normally do So these statements are really contradicting each for me! How and what should i eat exactly?? I really appreciate any advice or tips anyone can share. Thanks a lot!

Questionable Sanity

Two Big Macs, three times a day.