So there is no prerequisite knowledge ?
A desire to learn, helps to be logical.
buy a second board in case you destroy the first one
For the UNO, buy several controller chips as you will undoubtedly damage it/them (until you become proficient).
The IDE (Free Arduino development software package) has lots of examples with it.
Go though each and when you understand how each works you will become more competent.
You learn best by doing.
Also look at examples others have done to see how they solved problems.
Search for sites on the internet like this.https://learn.adafruit.com/category/learn-arduino
Pick up a book or two:http://www.amazon.com/Arduino-Teens-For-Course-Technology/dp/1285420896http://www.amazon.com/Arduino-Cookbook-Michael-Margolis/dp/1449313876
When you get stuck with something, ask for help.