It depends on what kind of art you want to create, and on how your mind works.
If you have your heart set on 3-D style renderings, you'll have to use Poser or a poser-like program and deal with the instructions in "Greek."
Photoshop is very popular. You will need a drawing tablet if you go that way, but the basic Wacom tablets come with Photoshop Express - a "lite" version of Photoshop. There are also various other "paint" programs more or less like Photoshop, ranging from free to cheap to not-cheap.
Photoshop is also used a lot by people who draw on paper, the old-fashioned way, then scan in their drawings and use a program to touch-up and color the result.
I use CorelDraw, because it matches the way my mind works. It's a vector-based program - it works by letting you create lines and shapes that you then can then modify in various ways. (As opposed to paint type programs that put smears of pixels on a virtual canvas.) I work by creating very rough shapes and lines ("block figures" - like stick figures, only... blockier) Then I smooth and bend the lines, and cut & weld the shapes, and adjust the colors, and add smaller shapes and lines for the highlights, shadows, and details.
Some people use both types of programs - vector type programs for some parts of their drawings, and paint type programs for other parts.
Abobe (makers of Photoshop) and Corel both offer free trial downloads of their programs. There are also various freeware alternatives: E.g. GIMP as a freeware paint program, or Inkscape as a freeware vector program.
http://www.techsupportalert.com/best_46_free_utilities.htm is a good source for free programs in general.