There's all kinds of resources now to learn :D if one video or article doesn't make things click for you, don't give up- just try a different tutorial author, because there's a million ways to solve the same equation in art.
i recommend doing practices from objects in real life. Anything, truly, but to start with try to find simple objects with not a lot of detail.... and really try to hone in on their colors and values. This helps teach you an overall grasp of form and how light bounces around a three dimensional space.
gesture drawings, and still lifes; in art school we would do regular drawings of thirty second "scribbles" of blind and partially blind gesture drawings (googling "how to do blind gesture drawing" should bring up tutorials) and honestly...
at first i thought it was silly. What was the point of rushing myself so fast i didn't get things 'right?'
but the more i did- the more i noticed that i got better and had less stress in making art in all my other mediums. It really helps teach you hand to eye coordination and an intuitive understanding of how different lines on the paper, create that illusion of depth and volume.
Color theory! Another fun subject to study especially if you want to add color to your art. "Ambient occlusion" is a great search word for tutorials on lighting and how to render it in digital art or other mediums.
if you're trying to learn something- don't be afraid to start small, and don't be discouraged if you don't prosuce what you think is the "right" artwork on the way to getting there. Every line you draw is gonna teach you muscle memory for the next time you draw.
that said, it's also helpful to draw wildly different subjects... and the same subjects but from very different perspectives, lightings, or forms (like a pony versus an arabian horse, or a terrier dog versus a maned wolf) because this will help you avoid falling into the trap of drawing the same thing over and over for every drawing.