How to implement init method in C

So I wrote the following header file VariableVector.h:

#define VECTOR_INITIAL_CAPACITY 20

struct _Variable {
    char *variableName;
    char *arrayOfElements;
    int32_t address;
};
typedef struct _Variable Variable;

struct _VariableVector {
    int size; // elements full in array
    int capacity; // total available elements
    Variable variables[VECTOR_INITIAL_CAPACITY];
};
typedef struct _VariableVector VariableVector;

void init(VariableVector *variableVector);

void append(Variable *variable);

Variable* find(char *variableName);

And in my VariableVector.c file I would like to implement all of the above methods but I do not know how.

#include "VariableVector.h"

void init(VariableVector *variableVector) {
    variableVector->size = 0;
    variableVector->capacity = VECTOR_INITIAL_CAPACITY;

    // allocate memory for variableVector??
}

void append(Variable *variable) {

}

Variable* find(char *variableName) {
    return NULL ;
}

can anyone offer suggestions?