https://www.letscontrolit.com/wiki/index.php/ESPEasy

Step 1 - Find the right flash size of your module
Step 2 - Download the zipfile here: espeasy_r120.zip
Step 3 - Double Click “flash.cmd”. A command windows should start with three questions.
Step 4 - Select the com port that your module or FTDI module is using
Step 5 - Select the flash size, 512, 1024 or 4096
Step 6 - Select the build version like 120 or newer.

When a fresh ESP Easy module boots up, it has no Wifi config and it will start as an Access Point. Use a Wifi enabled device (Laptop, Tablet, Smartphone,..) to search for Wifi access and try to find an access point with the name ESP_0.

Connect to this access point with default password: configesp

Launch your internet browser and it should find the captive portal hosted by the ESP module.