Step 1: strengthen your stabalizers, that is, the muscles protecting your back and spine. this would include stretches and light resistance training.
Step 2: strengthen your core muscles, that is, your abs, sides, and back.
Step 3: strengthen your upper body and lower body, each muscle group included, the main ones being:
chest
triceps
biceps
shoulders
back
calfs
glutes
hamstrings
quadriceps
Step 4: create a routine that you stick to, whether it is everyday or once a week, and STICK TO IT. introduce cardio and more stretching, and never forget to work EVERYTHING EQUALLY.
You could probably do steps 1 and 2 at the same time.
You can find many, many workouts online. Once you've started getting a feel for what you need to do to get the results you want, you can start writing your own workouts. You can message me on FB if you want to talk more about specific things man