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 <email@example.com>
* 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
* 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
// Enables and select radio type (if attached)
#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_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
// Setup locally attached sensors
// Present locally attached sensors here
// Send locally attached sensors data here