Sample code for the CryptGenRandom function.

CryptGenRandom.cpp

#include <iostream>
#include <windows.h>
#pragma comment(lib, "advapi32.lib")

int main()
{
	HCRYPTPROV hProvider = 0;

	if (!::CryptAcquireContextW(&hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
		return 1;

	const DWORD dwLength = 8;
	BYTE pbBuffer[dwLength] = {};

	if (!::CryptGenRandom(hProvider, dwLength, pbBuffer))
	{
		::CryptReleaseContext(hProvider, 0);
		return 1;
	}

	for (DWORD i = 0; i < dwLength; ++i)
		std::cout << std::hex << static_cast<unsigned int>(pbBuffer[i]) << std::endl;

	if (!::CryptReleaseContext(hProvider, 0))
		return 1;
}

You need to add
#include <Wincrypt.h>
as well