Squats. Heavy squats....but you are a novice, you need to put form ahead of weight. Form is seriously super important in all exercises, but especially leg stuff and shoulder stuff.
Squats and a good diet is the best you can do. You can add other stuff, but without the squats you are just wasting your time.
Squats, diet, plenty of rest.
Finding what works for you, you will figure it out.
But something like squats: 10 reps
all at your max, (the most weight you can do for that amount of reps) is good, with 2 to 3 mintues of rest inbetween each set. Course, you need a good warm-up and need to learn how to safely use the equipment.
You must use safety bars, it's just silly not to. Even if you have someone with you, there is no need to rely on them.
A good stretch routine at the end of your workout is good. Do you stretch well?
100 percent safety and form first. You can seriously mess up your back/knees if you learn bad form and/or don't workout safely.
You're a fitness novice, which means you are going to grow no matter what you do at first, as long as you have a decent diet. Now is the time to learn good form first.