How to create an empty doubly-linked list in C?

Question

I wrote most of the code for my doubly linked list in C, but it seems that the reason I'm struggling to add values into the list is due to a mistake I made when creating an empty doubly linked list. Here's my attempt at it, what am I doing wrong here and how would I go about fixing it?

struct node
{
    struct node *next;
    struct node *prev;
    char *value;
};

// The type for a list.
typedef struct list
{
    struct node head;
} List;

// The type for a list position.
typedef struct list_pos
{
    struct node *node;
} ListPos;

List *list_create(void)
{
  List *lst = (List*)malloc(sizeof(List));
  if(lst == NULL)
  {
    printf("No more memory!\n");
    return 0;
  }

  return lst;
}

static struct node *make_node(const char *value)
{
  struct node *result = malloc(sizeof(struct node));
  result->value = strdup(value);
  result -> next = NULL;
  result -> prev = NULL;
  return result;
}

---

Example usage: main function: List *lst = list_create(); from function add_values():

static void add_values(List *lst) {
  char str[2] = "A";
  ListPos pos = list_first(lst);
  for (char ch = 'A'; ch <= 'Z'; ch++) {
    str[0] = ch;
    pos = list_insert(pos, str);
    pos = list_next(pos);
  }
}

Implementation of functions:

int main(void){
List *lst = list_create();
...
}

add_values static void add_values(List *lst) {     
char str[2] = "A";     ListPos pos = list_first(lst);     
for (char ch = 'A'; ch <= 'Z'; ch++) {         
str[0] = ch;         
pos = list_insert(pos, str);         
pos = list_next(pos);     
 } 
}