I'm going to be brutally honest, just do press ups if you want to be able to do them. I could barely lift my own weight before I joined the RAF and now I'm doing 65 diamond press ups in a minute now. Just practice. Do 5, let your body rest for a day and repeat 3 times over (ie 6 days), then increase your reps by 3 and do another 6 days. You can't just go down the gym and bulk up unless you know what you're doing, know what muscle groups you need to target and then how to allow your body to increase muscle mass. It takes time.