Everyone, except for a very few very weak people already have a ‘six pack’. The muscles are there, they’re just covered by fat on most of us. So to answer your question you should concentrate more on loosing the fat then gaining muscle. Although if you want to work your abs the best way will always be sit ups.
If you reduce your caloric intake to less than you spend in a day, you will lose weight. If you exercise as well, you’ll lose it a bit faster. The best type of exercise is running or biking, you’ll burn a lot of calories doing that. Sit ups, push ups, or weight lifting will build muscle, but burn few calories. You don’t need to add too much muscle. You need to lose the fat on your belly, which can be that hardest part to lose.
Stick to a good diet and do sit ups when you can and you’ll get there soon enough.
