I'm guessing that to join you need to be able to run, and do a certain number of pushups / pullups.
You can do it a few ways tbh
Monday go for a run
Wednesday. Yeah you guess. Go for a a run
Friday, go for a run
Tuesday. Do 3 sets pushups 3 sets pullups 3 sets crunches / optional 3 sets leg raises
Thursday 3 sets bench press , do sets of 10 , 3 sets of a back exercise but tbh May aswell just be pullups
3 sets for core
Saturday 3 sets pushups , 3 sets pullups , 3 sets for core
That's all you need to do.
If your fat, cut, keep running just go and jog 20-30 minutes stay consistent for 2-3 months then you should lose weight and start to see some ok running gains. When you can run for a good 30 minutes and push yourself to finish fast then it's time to start specific running training to do the 2miles or whatever it is you have to do in a good time.
If you currently have muscle, good luck and try to keep it! Because I started training to join the army as a skinny kid, and in still a skinny kid. But now I can run far, 12 wide grip pullups, and about 45 pushups. Should be joining militsry as soon as a Injury heals up and I can get back to running
