Copied from https://www.instructables.com/id/Raspberry-Pi-Bluetooth-to-PuTTY-on-Windows-10/ First part: https://gist.github.com/deeja/83f50fb893383ba328e06769a1e6d44d
First configure you Raspberry Pi for Bluetooth shell access, by following the directions in Patrick Hundal's article Headless Raspberry Pi configuration over Bluetooth.
Notes on this process:
As an alternative to SD Card pre-configuration, the method I used was to enable the Pi's serial port, login using the PuTTY terminal program via a USB to serial converter, and configure the Pi's system whilst it ran on the target hardware. There are many other instructional articles available on this topic.