You need to know how to use the Sharepoint client object model. Firstly, you have to get the SP Context ->  SP List -> SP ListItems.

Here is the complete basic operations using JavaScript Object Model code in SP. I think that will be really helpful for you: 
[http://msdn.microsoft.com/en-us/library/office/jj163201.aspx][1]


  [1]: http://msdn.microsoft.com/en-us/library/office/jj163201.aspx