Development boards such as the Lolin NodeMcu V3 Module probably have the AT Command firmware loaded. Connect the development board to the computer USB port with a micro USB to USB cable (aka mobile phone cable). Then use [[https://esp8266.ru/esplorer/#sthash.RTeNSDvz.dpuf|ESPlorer]] with latest Java to test. Select the COM port, Select 9600 baudrate, then Click "Reload" or "FS Info". Select the AT-based tab and try the AT and GMR buttons. 

You can go to [[http://www.agcross.com/2015/09/the-esp8266-wifi-chip-part-3-flashing-custom-firmware|The ESP8266 Wifi Chip: Part 3 – Flashing Custom Firmware]] to learn how to flash other firmware. With the Micro USB to USB cable connected, skip down to **FLASHING NODEMCU** and flash your firmware of choice.