Hello Guys, What should i write in vApplicationStackOverflowHook ? could you give me an example?

What do you want the overflow hook to do? If you just want to halt the system then disable interrupts and sit in an infinite loop so nothing else can run. If you want to know which task overflowed its stack then either print out or otherwise store the task name and/or handle that are passed into the overflow hook function. What you should not try and do is recover from the stack overflow though - if you need to do that then use an MPU port instead as that will alert you before the overflow occurs rather than afterwards.