I learn to have a proper form by feeling for what works right with my body and what makes me feel as if i am having a challenging workout but at the same time not uncomfortable for my body.
Мишка Романова N.
You can seek help from a trainer or someone who has been doing those exercises for a long time, if neither options are available you can use youtube! Good luck <3
I usually use applications for at-home workouts and the exercises are all paired with a video demonstration as well as written instructions on what the exercise should look like, which muscles it’s targeting, form errors to look out for, and even possible modifications to be made.
I think also by time you can feel it in your body when a particular exercise is really activating the targeted muscles or not via your form.
You could also always have a couple of PT sessions at your nearest gym, if this is a feasible option, to learn the basics of a correct form during exercises and then continue on your own once you have mastered them.