What type of skills does one need in order to create Digital Art?
First of all you need to know what you have to create. Then you need to have knowledge about the different graphics tools to let you decide which tool will be better to achieve your goals. To first try to learn the popular graphics tools by trying basic to advanced step by step tutorials. One you have strong know-how about the tools you can easily create any graphics art you like.
Digital art is like any other form of art. Photoshop is merely a tool which most people can learn how to use in the same way that you can learn how to use paintbrushes. The same prinicples of design, form, tone, perception apply as with any visual art.
Have a look at deviantart.com there are great digital arists there, lots of free stock photos and many good tutorials.