Basic exercise questions from a newbie

AilinaHavalii

So let me start this out by saying that I've been reading through the forums and I've even taken some time to attempt to study in other places online, but I find myself completely overwhelmed by the massive amounts of information, specific and generalized, and I thought I'd ask for help here. This is my very first post here, so please be gentle. So here goes:

I'm a 22 year old female, 5'2", 120 lbs, so not trying to lose weight, numbers-wise (I started out at 155 when I got on MFP, and got down mostly through counting, with minimal exercise). Unfortunately, I am fairly sedentary, and thus am still unhealthy regardless of the number on the scale. I do 42 minutes of cardio (elliptical, while watching House episodes, hence the exact number) approximately 5 times a week, and burn ~250-300 calories each time (depending on how hard I push, and going from the machine's reading, not MFP's). I used to run, but I found it to be hard on my knees, so I switched to the elliptical, which helped. I carry most of my excess fat in my stomach, which, besides being a massive insecurity point for me, is also apparently the kind of fat storage that leads to the most health problems later in life, so I'd like to do something about that (I know that targeted area weight loss is not a thing, hence the desire for overall improvement). Also, regardless of the cardio I am doing, I don't seem to be feeling any healthier or having more stamina.

I am about to move somewhere where I will have easy access to a full gym, and I want to actually do something to get "toned" and to gain some muscle and definition. My problem is, I have absolutely no idea where to start. I have never actually been in a real gym like this before, and I'm fairly anxious about just walking in with no idea what I'm doing. I hear people talking about "doing weights," for example, but I have no idea precisely what that would entail for me. I've tried to read some of the posted guides here, but as previously mentioned, they either have so much information as to be overwhelming, or they talk as if I should already have a basic understanding of what they're saying (which I very much don't).

Based on what I have described about myself, does anyone have any (detailed) information about how I should go about starting an actual fitness regime? My main goals are, in order of importance:
Improve stamina and general health
Tone stomach area
Actually gain some form of butt (my pants fall down even with belts, it's absurd)

Also, any information about exercise-specific dietary needs would be helpful (I keep my calories in check, but I'm fairly clueless about macros, and I would have no idea what I'd have to compensate for when doing more exercise. I've seen some mention of protein, I think, but I'm unsure if I'm supposed to get more when exercising or just keep up with my suggested goal).

Thanks for reading this ridiculously long post, and I appreciate anything you all can do to help me out!

ninerbuff

Improve stamina and general health

Intense exercise with short rest times.

Tone stomach area

If you're referring to losing belly fat, that comes with calorie deficit.

Actually gain some form of butt (my pants fall down even with belts, it's absurd)

Full squats, glute bridges, deadlifts.

Start a basic program with just one exercise per body part and learn and nail down the form. 3x10 reps with weight that you can do exercises correctly with.

A.C.E. Certified Personal/Group FitnessTrainer
IDEA Fitness member
Kickboxing Certified Instructor
Been in fitness for 30 years and have studied kinesiology and nutrition