@wemchud quickly clarifying, you don't want to lose weight, you want to change your fat to muscle ratio. The number on the scale will hopefully go up in your ideal scenario where you're bottom half grows. To become leaner you simply eat less while still working out, this does not mean starving yourself or skipping meals! It important to still have enough protein. The best diet you can do is lots of chicken, fish, sweet potatoes, a fuck ton of veggies, and some good ol' carbs, I would throw in a protein shake, multi vitamin, and creatine to fill in any gaps. Protein per day for you would be 92-130 grams per day (a gram per pound is a quick mental note, but the science is showing 0.71 grams of protein per pound of body weight is enough to grow, particularly if you're young and healthy).
That said it is really hard to GROW while also becoming leaner. This is why people bulk then cut. A bulk is simply eating more while still working out. Don't dirty bulk, which is just eating fucking anything. Eat what I suggested above, just more of it lol (but also if you're bulking it's waaaay more okay to cheat the diet). At the end of the day if you don't want to overthink it just eat until you're full and making sure you have veggies / proteins on your plate, especially if you've had even an inclination of an ED in the past.
For growing your bottom half the two most important things are eating enough and not overworking yourself. The butt and legs contain the largest muscles in the body, those take time to repair after being worked. You're in luck though because women recover faster than men. I'd suggest doing lower body 3 days a week with a day in between each. Listen to your body, if your legs are still sore don't wreck them again, either take it easy or do a different muscle group all together.
Weight Squats are your best friend, you can also do bulgarian split squats to really target the quads / workout any imbalance, some people swear by hip thrusts and they're good for hips/glutes but have limited ROM, for really functional strength you can try deadlifting which will hit tons of different muscles, and of course there are good old fashion stairs. Do at least one day of cardio per week, but don't do a ton of cardio when you're doing lifts on the same day, it can be too fatiguing.
Deadlifts and Squats are particularly fatiguing because they're compound lifts (meaning they hit many parts of the body), so make sure to rest enough after those.
If you're new to using weights then watch a ton of form videos, practice a bunch with zero weight, then practice with light weight, then try heavier. Always warm up by doing the exercise with light/no weight. Try out different rep ranges and figure out what works for you. For me I like to do 3 sets of 7 reps some days, and then 5 sets of 5 reps others.
Feel free to hit me up if you have any questions
TLDR
Bulk by eating more (still healthy foods), grow by doing weighted squats and resting (which means good sleeps and good foods), get lean by eating a little less (but still healthy) and upping the cardio a bit. Aim for 3-4 days per week of working out, but listen to your body if certain parts haven't recovered yet.
Good luck!