beginning strength training or Olympic Weightlifting
Check out the beginning strength training method. There are coaches around if you're in a metropolitan area. Or check out an olympic weightlifting gym near your area. They'll accept anybody b/c its underused and its one of the fastest/researched ways to Make gains possible. All the fitness stuff you see online is loud noise. Plus Calorie surplus too, gotta bulk before you cut
Get enough nutrients and have a good workout that works the muscles you are trying to build. If you are just trying to improve your all around strength in every part of your body I would say the best way is to go swimming a few days a week. Do a lot of butterfly if your trying to work your lats and shoulders.