1
Plug in your adapter via USB and make sure no serial monitor (e.g. Arduino IDE) is currently connected to the COM port.
2
Click Flash Firmware below and select your device's COM port from the browser dialog.
3
Wait for the flash to complete. The adapter will reboot and broadcast a WiFi access point you can connect to for setup.
RS485-WiFi-EPEver — ESP8266 (D1 Mini)
Close any application using your device's COM port before flashing, otherwise the browser won't be able to connect.