How use multithread in verifone vx520?

Question

How can I use threads in Verifone vx520?

I want to use the code below but do not know what is int routine or int parameter or int stacksize and where should I specified my thread such as print a receipts while showing a message on-screen and how should to use them?

Should I download them in different group?

run_thread(int routine, int parameter, int stacksize);
thread_join (int thread_id, int *retval);