Not able find the library #include<PRIVATE.h>

I am not able to find the library " #include <PRIVATE.h>" in the registry.

I think you’re misunderstanding some example code. It probably wants you to create that header file yourself and add in the needed private details for the sketch to work (WiFi, password, keys, whatever…).

Can you link to the sketch you’re using?

#include <Arduino.h>
#include "FS.h"
#include <LITTLEFS.h>
#include "MyOCPPImplementation.h"
#include "MyArduinoWebsocketsAdapter.h"
#include "OCPPCore.h"
#include "MyRequestHandlerRepository.h"
#include "SentMessageRepository.h"
#include "HeapDebug.h"
#include "PRIVATE.h"

// Create connection address
String connectionURL = String(URL) + String("/") + String(STATION_ID);
WebsocketServerAddress wsAddress(HOST, PORT, connectionURL, OCPP_VERSION);

// We store the default callback for each message here
// You can define the callbacks in 2 places:
// - the MyRequestHandlerRepository.cpp file
// - at the creation of each message, in the constructor of each message
MyRequestHandlerRepository *reqHandlerRepoPtr = new MyRequestHandlerRepository;

// For storing messages that are waiting for a reply from the CSMS
SentMessageRepository *sentMessageRepoPtr = new SentMessageRepository;

// Create the message handling implementation
OCPPEventHandlers *eventHandlersPtr = new OCPPEventHandlers(sentMessageRepoPtr, reqHandlerRepoPtr);

// Create the OCPP websocket class, inject the message handler implementation as a dependency
MyArduinoWebsocketsAdapter *myWsAdapterPtr = new MyArduinoWebsocketsAdapter(wsAddress, eventHandlersPtr);

// This is where we define the main communication loop and create messages
MyOCPPImplementation *myOCPPImplementationPtr = new MyOCPPImplementation(myWsAdapterPtr, sentMessageRepoPtr, reqHandlerRepoPtr);

// Put all of the above into one class
OCPPCore OCPP(myOCPPImplementationPtr, myWsAdapterPtr);

void setup()
{
  USE_SERIAL.begin(115200);
  USE_SERIAL.setDebugOutput(true);
  delay(100);

  OCPP.setup();
}

void loop()
{
  // DEBUG_LN_HEAP(2000);
  OCPP.loop();
  vTaskDelay(1);
}

Well an obvious candidate for the content of the PRIVATE.h header file would be to define all those captalized macros.