struct Stack
{
    Node *top;
    List *data;
    int   size;
};

Stack *mkstack (int);

The guts of your mkstack function should be relatively simple, including but not limited to:

• Allocate the appropriate memory
• Assign myStack→data to be your list of choosing
• Assign myStack→top to be one end of your list
• Assign the appropriate value to myStack→size

Stack *rmstack (Stack *);

Much like rmlist from previous adventures.
You may want to run a few functions to handle the underlying list prior to handling the stack, as in this case the stack is built upon the list.
We don't want a list if we don't want a stack

Stack *pop (Stack *, Node **);

As stacks are always manipulated from the top you'll want:

• obtain myStack→top
• re-assign myStack→top

So long as your stack top isn't NULL that is

Stack *push (Stack *, Node *);