Elements would be earth, air, fire, water and if you count soul or spirit as 5, then that one as well. Shadow isn't an element, it's a lack of light. It's darkness. Darkness normally represents evil or ignorance. (ignorance isn't evil, so darkness isn't always "bad.") Some use darkness to describe something they see as good that others generally see as bad.
It may be easier if you list the things you want to do with "shadow magic." The way you are talking it sounds like you want to learn the way of the ninja, hiding in shadows or something, or dark magic.
This is what I tell anyone wanting to learn any kind of magick:
First learn that magick works from the inside out. Second, to take control of what goes on out side yourself, you must first take control of what goes on inside of you. Third, you take that control by practicing every day. Lastly, you are always where you should be, don't rush the path. Magick of any kind comes from you learning how to control and manipulate your chi, or chakra or your energy. The best way to do this is through meditation. Once you control the flow inside of you, you can start using it to control things outside of you.
Hope that helps, if you want something more specific, please be more specific.