Losing weight to join the Navy!

Hey guys, I used this app before, and it seemed to help me. But I have gained weight since I stopped and I moved, but I've moved back to Hawaii and it's time for me to prepare to join the navy. I have to lose at least 15lbs to join but I'm going for 17. I already blow the navy requirements for a 1 1/2 mile run time out of the water. But I'm working on the push-ups and sit ups. I'm doing other excersises to help strengthen those muscles. Any tips would be taken with much appreciation! Good day everyone!