Installing the firmware .bin files to the various ESP32 boards is now pretty simple. The easiest is using Adafruit's online browser-based flasher here:
https://adafruit.github.io/Adafruit_WebSerial_ESPTool/
This uses 'WebSerial' which you may need to explicitly allow, via the browser's settings, and/or allow 'experimental' features. This is explained here:
https://learn.adafruit.com/adafruit-magtag/web-serial-esptool
When you connect your ESP32 board via USB, and press 'Connect' in the top-right, you can then specify which partitions to overwrite. The factory default partitions are usually fine. In extreme cases you may need to restore the bootloader and other system partitions before uploading the main 'application' partition. (Shout out if you find yourself in this situation, because it's too complicate to describe here).
The main 'application' partition is at offset 0x10000. So, you enter that in the top item, then click Choose File, and select the .bin file you have on your local file system. You then click the on Program button and the upload will commence. You should see a screen like this:
Just wait for the progress bar to complete. When all finished, unplug then re-plug in the board to reset it (or press the 'reset' button).