One implementation might store the data in a linked list, while another might store the data in a dynamically allocated array. For this assignment, we will use a dynamically allocated array.
Every time I read an assignment that asks for a student to use a dynamically allocated array (especially when pointing out a standard container works just as well), a puppy dies.

Any ways, there is not much we can do for you if you don't understand what to do after having read about RPN. We can help with the code, the code logic, or just getting you started, but you need to input the actual logic behind what you want to do.