Working with linked list whose member is a binary search tree (BST)

Question

I am new to C data structures and I am working with a linked list and a binary search tree. The linked list is composed of 2 members, a string type and a binary search tree type. Here is its definition:

typedef char *String;
struct LinkedList
{
  int employer_id;
  EmployeeBST employees;
  struct LinkedList *next;
  
} *LinkedList;

struct list
{
  ListNodePtr head;
} EmployeeList;

The employee BST definition on the other hand

typedef char *String;

typedef struct bstNode
{
  String employeeName;
  struct bstNode *left;
  struct bstNode *right;
} *BSTNodePtr;

typedef struct bst
{
  BSTNodePtr root;
} EmployeeBST;

I want to insert new members to the linked list, here is my insert function

struct listNode *newListNode(String unit_code, EmployeeBST employees)
{
  struct listNode *newNode;
  newNode = malloc(sizeof(struct listNode));
  newNode->employer_id = 89;
  newNode->employees;
}

The problem is what value should I assign to the newMode->employees? I have the insert function for the BST which is implemented as:

struct bstNode *insert(struct bstNode *bstNode, int employer_id)
{
  if(bstNode == NULL)
  {
    return newBstNode(employer_id);
  }
  // traverse right and insert the node
  if(employer_id < bstNode->employer_id)
  {
    bstNode->left = insert(bstNode->left, employer_id);
  }else
  {
    bstNode->right = insert(bstNode->right, employer_id);
  }
  return bstNode;
}