I use Photoshop with a small wacom tablet. Just about all my work in
the last dozen years has been done on a computer.
It takes a bit of practice to do digital art, but once you get it down
it's not hard at all. One can draw with a mouse, but I never was able
to do very well with one. I would recommend a drawing tablet. You
can get a small wacom tablet for around $60..
Some feel they need a large tablet to be able to do details, but
I just enlarge the work for details.
There are a few free paint programs out there. Just google for them.
Good luck.