I only got connection on tx, rx and ground on the pin header you connected to.
Don’t know why, but could’nt find a connection from those pins to the ESP.
So i think you need to do it like in the picture on github.
So TX , RX and Ground on the pin header as you have.
3 volt and IO0 directly to the ESP pins.
I just held them in place during flashing.
Just find a steady way to do it if you do it this way.
You can solder them if you feel safer that way
Should be fine with what you have.
Just do TX to RX and RX to TX.
And remember, be shure it’s 3volt and not 5 volt.
Some adapters have a switch for that i have seen
Don’t ask me how I know, but it can be dangerous to flash custom firmware on the non-2.0 genies (the ones with a built in battery). Without the proper precautions, you might end up breaking the 5V regulator.