I'm going to talk you through how to properly do a squat. There's a million different ways of doing a squat. I'm just going to show you the basic body weight squat, meaning you don't have any weight that you're working with except yourself. As you get stronger, you might want to progress - holding a medicine ball, holding a weight, or even holding your kid, anything that's going to add weight to your legs. This is predominantly a lower based exercise so you're going to focus on your quadriceps muscle groups, your gluts, your hamstrings, and your whole posterior chain. Basically, all of the muscles of the lower body are going to be working in this exercise.
You want to start with your feet probably about shoulder width apart. If you're more comfortable a little wider or even externally rotating your fit a bit, just find place that's comfortable for your hips and make sure that your knees always track. A good rule of thumb is to think about your knees going right in between your big toe and your second toe. When you're doing a squat just watch out that your knees are not adducting and collapsing in or abducting and going out. You want to try to maintain the knee in a neutral position
The wider you are too, the easier it's going be to balance. If you have stability issues, start wide. If you want to challenge the stability, then you bring your legs a little closer together and challenge your core muscles by challenging your balance.
So, standard squat, shoulder width. Something comfortable. You're going to imagine like you're sitting back into a chair, lengthening your spine, reaching your hips back, bending your knees, and then exhale to come up. You're always going to inhale as you lower your body and you're always going to exhale as you lift any weight. In this case, the weight is your body. Exhale, pull the abs in, and come up to vertical tall spine.
My tips for the squat, again, aside from the knees is what's going on with your spine. I'm going to show you from the side. If you're facing side you could look at yourself in a mirror and watch your positioning if that helps you when you're first learning. Same thing, sitting back like you're sitting back into a chair and watching that your spine is neutral. That means I'm not doing hyper extension, and I'm not doing excessive flection. I'm just trying to be right in between. You have natural curves to your spine, so you want to maintain those, so nothing excessive forwards or backwards of that. Then just do as many reps as you can do, maintaining good form, breathing in on the way down, exhale on the way up, targeting all the major muscle groups of the lower body.