There is lots of info on this elsewhere, but this is partly for me to easily find when i forget :)
Grab the esp8266 firmware flasher and binary, i used v0.9.2.2 AT Firmware.bin from here
use a low numbered COM port , 6 or less, you can change this in the device manager if needed, in windows handling comports about COM10 is slightly different so a lot of software won't do it
power on the esp8266 with serial at 115kbps
Run the flash tool, load the binary change the COM port to match, leave the second number (offset) at 0x0000 )
Hit download, should see this, I've always gotten the last warning.
Writing at 0x00000000... (0 %)
Writing at 0x00000400... (0 %)
Writing at 0x00000800... (0 %)
Writing at 0x0007e800... (99 %)
Writing at 0x0007ec00... (99 %)
Failed to leave Flash mode
After flash the ESP8266 settings will likely reset to 9600n81, enjoy new baud rates etc!, remove power , remove GPIO low , and restart.
AT+GMR prints the firmware id
Set the baud rate
Listen on UDP port 20002
Some other notes, the cypress bootloader host has a couple of small bugs, if you remove board to switch into bootloader mode, it'll redo the com port list and reset to the first entry. if you have the comport open in another app, it'll null out all the settings and then back to 9600 after closing the other software using the com port
With teraterm (maybe others too ) i can remove the dev board from usb and plug it back and in and it'll keep the serial going, which is really useful and acts more like a traditional RS232 port. But it also means i forget to close teraterm and the bootloader issue above kicks in, be nice to have a cmd line bootloader going instead or just have the uart bootloader integrated into the Creator UI.