This this video how to start using Heltec ESP32 WiFi OLED, Bluetooth Microcontroller baord.
00:40 Introduction
01:04 Hardware Explained
02:19 Preparing Arduino IDE for this board
04:52 Sample Code (1)
06:40 Sample Code (2)
07:40 Sample Code (3) Bargraph
08:44 Sample Code (4) Interface
09:22 Sample Code (5)
The link to use in the "preferences" of Arduino IDE for Heltec ESP32 board
http://resource.heltec.cn/download/package_heltec_esp32_index.json Watch video for instructions.