@mrussi
Not sure if you still need this info, but I'll leave it here in case anyone else needs it. I couldn't find this either so i had to look at the heltec pinout diagram and compared to the ESP32 Library
/*
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2018 Sensnology AB
 * Full contributor list: https://github.com/mysensors/MySensors/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - tekka
 *
 * DESCRIPTION
 * The ESP32 gateway sends data received from sensors to the WiFi link.
 * The gateway also accepts input on ethernet interface, which is then sent out to the radio network.
 *
 * Make sure to fill in your ssid and WiFi password below.
 */
// Enable debug prints to serial monitor
#define MY_DEBUG
// Enables and select radio type (if attached)
//#define MY_RADIO_RF24
//#define MY_RADIO_RFM69
#define MY_RADIO_RFM95
#define MY_DEBUG_VERBOSE_RFM95
#define MY_RFM95_RST_PIN 14
#define MY_RFM95_CS_PIN 18
#define MY_RFM95_IRQ_PIN 26
#define MY_RFM95_IRQ_NUM MY_RFM95_IRQ_PIN
#define MY_SOFT_SPI_MOSI_PIN 27
#define MY_SOFT_SPI_SCK_PIN 5
#define MY_RFM95_FREQUENCY (RFM95_868MHZ)
#define MY_RFM95_MODEM_CONFIGRUATION RFM95_BW125CR45SF128
#define MY_GATEWAY_ESP32
#define MY_WIFI_SSID "WiFi_SSID"
#define MY_WIFI_PASSWORD "password"
// Set the hostname for the WiFi Client. This is the hostname
// it will pass to the DHCP server if not static.
#define MY_HOSTNAME "ESP32_GW_LoRa"
// Enable MY_IP_ADDRESS here if you want a static ip address (no DHCP)
//#define MY_IP_ADDRESS 192,168,1,100
// If using static ip you can define Gateway and Subnet address as well
//#define MY_IP_GATEWAY_ADDRESS 192,168,1,1
//#define MY_IP_SUBNET_ADDRESS 255,255,255,0
// The port to keep open on node server mode
#define MY_PORT 5003
// How many clients should be able to connect to this gateway (default 1)
#define MY_GATEWAY_MAX_CLIENTS 2
#include <MySensors.h>
void setup()
{
	// Setup locally attached sensors
}
void presentation()
{
	// Present locally attached sensors here
}
void loop()
{
	// Send locally attached sensors data here
}