If you don't want to compile CircuitPython you can just load the most recent build using UF2 with drag-n-drop.
Click here to find the latest build:
Click the directory for your board...
By default the newest build is at the top. Check the two letter code for your language: english, espagnol, french, filipino (tagalog) - we'll be using the english build but instructions are the same for other languages.
Enter the nRF52840 bootloader by double-clicking if it isn't already in bootloader mode, then drag the UF2 file to NRFBOOT
You'll see a new disk drive CIRCUITPY