Don’t overthink it or over complicate things. Search this place for quality advice. Especially @Coachmikechadwick
Get out and make sure you are running 3 or 4 times a week, a mix of shorter faster best effort runs and longer slower steady state runs. Throw in hill sprints and interval training and some good high intensity body weight circuits. Be able to smash all the entry requirements and then in the gym work on building your strength and power. The training is progressive so don’t talk yourself out of it. No one will ask you to do P Coy on day one. Just have a good attitude and a good healthy base level of above average recruit fitness and let 4 PARA do the rest!