USB shield – usb host shield
if you will not use External Power please be sure this jumpers are soldered as below :

so after soldering it will be like this image

Dip Switch 2P 1 × 4SAR
ESP8266 _ ESP-01 based on ESP8266 WiFi Module 1 × 35SAR
MQ-2 gas sensor 1 × 33SAR
LilyTiny LilyPad CJMCU for Arduino projects 1 × 41SAR
Prototype Shield for Arduino MEGA 1 × 35SARSubtotal: 148SAR
Dip Switch 2P 1 × 4SAR
ESP8266 _ ESP-01 based on ESP8266 WiFi Module 1 × 35SAR
MQ-2 gas sensor 1 × 33SAR
LilyTiny LilyPad CJMCU for Arduino projects 1 × 41SAR
Prototype Shield for Arduino MEGA 1 × 35SARSubtotal: 148SAR
if you will not use External Power please be sure this jumpers are soldered as below :

so after soldering it will be like this image

All Electronics Components
All Electronics Components
All Electronics Components
All Electronics Components
All Electronics Components
All Electronics Components
All Electronics Components
All Electronics Components