I guess it depends on the art style. But generally, if you want to do it the hard way:
Get a drawing tablet. The ones where you draw directly on a screen are the best, but they are also way more expensive.
Get some powerful software that can imitate brushes. Krita is good.
Practice, experiment, watch videos and gather knowledge on both the art style and your software of choice. Copy pieces of art in the style you want to reproduce until you master it.
With an emphasis on the third point. Digital art done manually is not so different from traditional art - it takes practice.
Of course there are also styles you can reproduce using filters in GIMP or whatever. And you can do the above by drawing over pictures you’ve taken or borrowed for the purpose. It’s really a question with an unlimited number of potential answers.
I guess it depends on the art style. But generally, if you want to do it the hard way:
With an emphasis on the third point. Digital art done manually is not so different from traditional art - it takes practice.
Of course there are also styles you can reproduce using filters in GIMP or whatever. And you can do the above by drawing over pictures you’ve taken or borrowed for the purpose. It’s really a question with an unlimited number of potential answers.