Hip Raises are one of the safest and recommended exercises to start out with when starting to strengthen back your pelvic floor and hip muscles.
In the lying position, the key object is to be able to raise your buttocks/hips from the floor, extending your hips in an upward motion. They way I describe it to my clients;
Pretend you have a piece of string connected to each side of the hip. The string is pulling your hips up towards the ceiling.
As you raise your hips, press your heels down to the floor and squeeze your glutes (buttocks). Pause for a moment at the top then slowly lower yourself back to the floor.
2 sets of 10 reps. Increase the reps once you feel stronger and confident in the movement.
**The only time a new exercise should be introduced/transitioned into is when the current exercise is mastered. You know when you have mastered that exercise when YOU can control that exercise and the intended muscle(s).