Navigate to the Seger downloads page and install the version of the J-Link Software and Documentation Pack for your operating system:
You'll also want to download a compiled bootloader binary (.bin file) for the board you're recovering. These can be found on the Adafruit/uf2-samdx1 repository:
If you want to install CircuitPython onto the UF2 bootloader, you'll need a board-specific .uf2 file. Click here to find the latest build for your hardware:
When the UF2 finishes downloading, move the file to your Desktop.
We'll leave this file alone and come back to it when we're ready to load CircuitPython onto our board's boot drive.