When you said "even the simple program of HELLO WORLD is not working in MPLAB SIM". I don't know what kind of problem you are facing. Compiler problem? IDE problem? Simulation problem? or all the three problems?
I guest you have problem with setting up the IDE and setting Up Language Tools. If so, the following links will help you.
Download MPLAB IDE User's Guide from:http://ww1.microchip.com/downloads/en/DeviceDoc/MPLAB_User_Guide_51519c.pdf
Doccument number: DS51519C
Read part 6 for MPLAB SIM Simulator
Also this tutor is good for you:http://www.kwantlen.ca/science/physics/engineering/APSC1299/files_for_lab/MPLAB_IDE_quick_start_g_51281F.pdf
This tutor will show you how the basic steps:
• MPLAB IDE Features and Installation
• Tutorial Overview
• Selecting the Device
• Creating the Project
• Setting Up Language Tools
• Naming the Project
• Adding Files to the Project
• Building the Project
• Creating Code
• Building the Project Again
• Testing Code with the Simulator
Or this tutor:http://www.fatihun.edu.tr/~martiklar/TeachFall2003/EE_475/mplabTutorial.pdf
It show you step by step in very detail.
Or you can use Yahoo search for "MPLAB IDE", you will see many informations.