Check the software for bugs and improve it if you think it's necessary. Maybe you want to add new features. Anyway, it's a good idea to test it on a breadboard before you start soldering. You can find the software I used for this project here. I modified the lua scripts and pushed it to my developer board.
Now it's time to flash the ESP-01 and upload the software from step 1.
First, solder connectors to the battery holder and attach one end to the on/off switch.