Install Arduino (latest, 1.8.10), clone this repo into Documents/Arduino and open it up in Arduino
File->Preferences and add board manager URL:
https://dl.espressif.com/dl/package_esp32_index.json
Sketch->Include Library->Library Manager
FastLED 3.3.2
WiFi 1.2.7 (I think this one is installed by default)
NTPClient 3.2.0
Plug in the clock to computer w/ Arduino using USB. You should only need to do this once, subsequent flashes can go over Wifi.
Tools->Board->Node32s
Upload Speed: 115200
Port: Look for a COM Port named 'Silicon Labs CP210x USB to UART Bridge' in Windows Device Manager
Flash Frequency: 80MHz
Edit to add wifi SSID and password, it's much easier to hard code it here than deal with autoconnect when you're modifying things.
With this all done you should be able to hit upload and it will take a minute to compile and upload it. The clock should start and you should be able to access http://epochclock.local in a browser if mDNS works on your network (it might take a minute to start resolving). Otherwise you'll need to find the IP and connect that way.
Once you can access in a browser, you can login with admin:admin and use the web interface to upload new code to it (as long as the last code you uploaded didn't break code uploading!). Use Sketch->Export compiled Binary and then look for the .bin file in the Documents/Arduino/RGBEpoch folder.