How do I get a bikini body?

I have 3 months to get into perfect beach shape for my grade's class day. I'm a teenager, 5'3'' and 130 lbs. I'm a bit bigger than I'd like to be, and I want to tone my muscles. I did cross country, so I'm good with running, but I don't have that much time after school each day. I need a quicker workout that that will make my abs and thigh muscles more pronounced over the fat. I don't want to giggle, please help me!