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/u/Indiebear445 gave you great answers to your questions, so read their post. I just want to expand on the tips for losing weight and getting boot camp ready.
I was ~210 & 5'6 when I decided to join. I needed to get down to 150 (req. at the time), so essentially drop 60lbs before going to MEPs. I had to make drastic and long-term changes to my diet & activity levels. Long-term being the key here. You will have a very difficult time if you take steps towards weight loss every other week or so.
I recommend checking out /r/LoseIt and /r/Keto. Keto is essentially a low-carb diet (yes, that means no bread or sugary foods) that triggers a fat-burning state in your body. It isn't kooky fad-diet crap, it does work, but don't think it is some easy magic super diet either.
Evaluate your activity level and come up with a plan. If you are fairly inactive currently, ease in to a fitness plan that will guide you towards higher goals. One of the worst things you can do is jump in to new activities that your body isn't accustomed to and injure yourself. I'd recommend a Couch-to-5K style program. There are countless apps/guides which can help you out. For muscular fitness, there are also apps like Just 6 Weeks that guide you through a plan to improve your push-ups/sit-ups.
Set goals. Both long-term and short-term. For the Air Force, you essentially need to accomplish a 11:57 1.5mile, 33 push-ups, & 42 sit-ups in order to meet basic training standards. You also must meet the weight requirements for your height. Those are your long-term goals. Short-term can be anything from lose 1lb, to jog 1 full lap, or 20 push-ups. Anything that is just out of reach can be a short-term goal. > It is much easier to reach the top of a ladder by going up each rung, rather than try jumping to the top.
Track it all. I personally use MyFitnessPal but there are other alternative apps. This helps you not only keep track of what you eat/how active you are, but gives you suggestions to lose weight. It has quite a few ads/IAPs unfortunately, but the bulk of the features are free.