Make sure your form is good, and pay attention to the many prehab articles on this site. Foam rolling, mobility drills, stretching, and corrective exercises are helpful for staying healthy.
Also make sure your form is optimal for powerlifting - i.e. benching with an arch and using leg drive, a wider than normal stance on squats, etc. There are some articles here that can help you out if you search for them.
Popular strength programs to look up across the internets:
Bill Starr’s or Madcow’s 5x5
Westside Barbell Method
Jim Wendler’s 5/3/1 routine
Sheiko routines (there’s one posted in an article on this site)
People are different when it comes to supplements. Some people take tons, others take none. Personally I would recommend initially trying creatine and maybe protein supplementation depending on what kind of food is available to you while in service.
A broad question gets a broad answer