How to debug Code in retail POS SDK with visual studio 2013 (Back end is AX 2012 R3)

Dear All

 I am customizing a function in retail SDK Triggers project I installed the SDK and it is working fine (it builds in VS 2013 without error, and I added some code, generated a Dll and test it in a test POS). now I am trying to debug a function in that project (the project type is a class library so I can't use function in the VS 2013 ), what I have done and didn't work is to open the debug menu is VS 2013 and choose attach to process and choose the POS.exe (the exe process of the test POS installed in the same machine that has the Retail POS SDK) in that menu. I tried to generated the scenario where the debugger should enter the function, but it didn't .

what I need to know is how to debug  function in the retail SDK?